The nation’s rapidly growing Latino population is one of the most powerful forces working in President Obama’s favor in many of the states that will determine his contest with Mitt Romney. But Latinos are not registering or voting in numbers that fully reflect their potential strength, leaving Hispanic leaders frustrated and Democrats worried as they increase efforts to rally Latino support.

Interviews with Latino voters across the country suggested a range of reasons for what has become, over a decade, an entrenched pattern of nonparticipation, ranging from a distrust of government to a fear of what many see as an intimidating effort by law enforcement and political leaders to crack down on immigrants, legal or not.

Here in Denver, Ben Monterosso, the executive director of Mi Familia Vota, or My Family Votes, a national group that helps Latinos become citizens and register to vote, gathered organizers around a table in his office and recited census data demonstrating the lack of Latino participation.

“Our potential at the ballot box is not being maximized,” Mr. Monterosso told them. “The untapped potential is there.”

More than 21 million Latinos will be eligible to vote this November, clustered in pockets from Colorado to Florida, as well as in less obvious states like Illinois, Iowa, North Carolina and Virginia. Yet just over 10 million of them are registered, and even fewer turn out to vote.

In the 2008 presidential election, when a record 10 million Latinos showed up at the polls nationwide, that amounted to just half of the eligible voters. By contrast, 66 percent of eligible whites and 65 percent of eligible blacks voted, according to a study by the Pew Hispanic Center.

That disparity is echoed in swing states across the country. In Nevada, 42 percent of eligible Hispanics are registered, while just 35 percent are registered in Virginia, according to Latino Decisions, which studies Latino voting trends.

Although Latinos do not turn up at the polls in the same numbers, relative to their population, as other ethnic groups, their overall numbers are growing so rapidly that they are nevertheless on the verge of becoming the powerful force in American politics that officials in both parties have long anticipated — an effect that would only be magnified should they somehow begin to match the voting percentages of other ethnic groups.

Mr. Obama’s campaign has seized on that as a central part of his re-election strategy, with an early burst of three Spanish-language television advertisements in four swing states, including Colorado, and voter registration drives in Latino neighborhoods.

“Hi, are you registered to vote?” Linda Vargas, 62, called out in English and Spanish to people walking into a public library on the outskirts of Denver as she sat behind a table stacked with voter registration forms.

This segment of the American electorate is by any measure sprawling, with near-explosive population growth in places like California and Texas and growing numbers in swing states like Arizona, Colorado, Florida, Nevada and New Mexico. Their presence in such politically important states has only fed the frustration of Latino organizers over their underrepresentation at the polls.

Matt A. Barreto, an associate professor of political science at the University of Washington and head of Latino Decisions, said the population growth had produced a higher Latino vote in every presidential election over the last decade, a number that had the effect of masking the political apathy of many Latino voters.

“The population growth has driven increases in the Latino vote every year,” he said. “But we still need to confront a registration gap that is quite significant.”

Jim Messina, Mr. Obama’s campaign manager, said Latino voters were a critical factor in the president’s re-election hopes. “Look, if we do our job right and have a good ground game, I absolutely believe that Latino voters can be one of the big reasons we win this election,” he said.

Officials in Mr. Romney’s campaign argued that he would cut into Mr. Obama’s Latino support by challenging his record on the economy, and how, they said, it had been particularly harmful to Latinos. Last week, the Romney campaign posted a Spanish-language advertisement on its Web site pointing to rising unemployment among Latinos.

“Understand the dynamic of this election: it’s about the economy and it’s about jobs,” said Joshua Baca, who is responsible for the Romney campaign’s Hispanic outreach. “Whatever the Obama campaign wants to do with regards to targeting Hispanic voters, that’s fine. Our message is going to be, ‘It doesn’t matter if you are Hispanic, if you’re a woman, if you’re African-American: it’s the economy.’ ”

Latino voters overwhelmingly support Mr. Obama over Mr. Romney, according to recent polls. The anger at Republicans for supporting tough immigration laws, like the one passed in Arizona last year, is powerful and potentially damaging to Mr. Romney after a Republican primary in which the candidates largely rallied behind that law.

Yet interviews suggest lingering concerns with what many see as Mr. Obama’s failure to deliver on promises to change the immigration system, as well as distress about his stewardship of the economy. Together, those forces appear to be producing a general wariness of government.

“They promise, ‘Oh, we’re going to do this for the Hispanic community, we’re going to do that,’ and we never get even half of the things that they promise,” said Derkis Sanchez, 51, an independent who lives in Miami.

Evidence of the lack of participation can be found across the West, and particularly in Colorado, a state that could be one of the most contested in November. In 2010, 114,000 of the 455,000 Latinos eligible to vote in the state turned out, a study by Latino Decisions found; 47 percent of eligible voters are registered today.

The number of Latinos eligible to vote nationally may overstate their actual influence. Of the 21 million, nearly 10 million live in California or Texas, which are unlikely to be in play in November.

And while an influx of younger voters is helping to push up the overall number, younger voters have historically been disproportionately uninterested in politics, a particular challenge in Colorado given that the Latino population is younger than the overall population. A Pew study found that one-third of the nation’s eligible Hispanic voters are between 18 and 29; but they make up just 22 percent of the overall population.

Arturo Vargas, the head of the National Association of Latino Elected and Appointed Officials, said his organization projected that 12.2 million Latino voters would turn out this November.

“But we do have a performance gap between Hispanic voters and non-Hispanic voters,” he said.

Many analysts argue that the demographic wave of Hispanic voters that began in California in 1994, with a backlash to a state voter initiative backed by Republicans that prohibited illegal immigrants from using public services, is now sweeping over Arizona and Colorado, and eventually will return even Texas to the Democratic fold.

“I believe long term all those states are coming on the map,” Mr. Messina said.

Democrats and Republicans have recognized the rising power of Latino voters for over a decade; advisers to George W. Bush had repeatedly identified Hispanics as central to building a long-lasting electoral coalition. But the Republican position has dropped sharply as the party has been identified with tough policies focused on illegal immigrants.

Republicans have also pushed to impose tough restrictions on voter registration, which Democrats and Latino groups attacked as a way to discourage Hispanics, among others, from voting.

“Our state government is kind of repressive against immigration,” said Alejandro Martinez, 32, a Democrat who lives in Nogales, Ariz. “They’re afraid to go out there and vote.”

Organizers meeting with Mr. Monterosso said they had encountered deep reservations among Hispanics across party lines.

“When I hear a lot of Latinos say they are U.S. citizens but they are not registered to vote, that makes me worried: we are not helping one another,” said Jose Sanchez, 24. “I’m seeing in our community a lot of frustration, a lot of anger, a lot of disappointment and a lot of fear. We have a president that promised so much to our community but has offered us really bad news.”

Mr. Monterosso, sitting quietly as Mr. Sanchez spoke, responded that Republicans had led the way in demonizing Latinos for political gain. “Every single attack on our community has come from the Republican side,” he said.

Just outside Denver, Daniel Lucero, the co-owner of a barbershop, said neither political party had paid enough attention to Latino voters.

“I would say the majority I know, maybe 10 to 12 percent of them vote,” said Mr. Lucero, 66. “The rest don’t care. They feel like politics doesn’t affect them.”

In Nogales, Barbara Gudenkauf, said many of her fellow Latinos “feel like their issues aren’t being addressed. ‘My vote is not going to count. Why bother to take the time off work if it’s not going to make a difference?’ ”

On a hot afternoon in Las Vegas recently, Leo Murrieta, the director of Mi Familia Vota in Nevada, drove to the Department of Motor Vehicles office in a Latino neighborhood and watched as his workers, voter registration forms in hand, stopped people outside the office.

“I have staff out in 10 places today,” he said. “There’s a lot of work to be done.”

The first USA TODAY/Gallup Swing States Poll since theGOP settled on a presumptive nominee shows big challenges for each side: Mitt Romney in generating enthusiasm and a personal connection with his supporters, and Barack Obama in convincing Americans he should be trusted to manage a fragile economy.

The president and the former Massachusetts governor start their head-to-head contest essentially even among registered voters — Obama 47%, Romney 45% — in the dozen battleground states likely to determine the election’s outcome. That’s closer than the lead of 9 percentage points for Obama in the Swing States survey in late March.

But the poll also finds a reversal in what has been a key GOP asset in the five previous battleground surveys taken since last fall: an edge in enthusiasm among voters. For the first time, Democrats are more likely than Republicans to say they are extremely or very enthusiastic about voting — a shift from a 14-percentage-point GOP advantage at the end of last year to an 11-point deficit now.

That drop is driven by Republicans who describe themselves as moderate or liberal, about a third of the party, even though the candidate widely viewed as the most moderate in the GOP primary field is poised to be nominated. Just 7% of moderate and liberal Republicans now say they are extremely enthusiastic, down from 24% in January and compared with 34% of conservative Republicans who feel that way.

“After a long and completely negative Republican primary on the other side, there are not a lot of people enthusiastic about Gov. Romney,” Obama campaign manager Jim Messina said in an interview. “The polls are finally catching up to what we’re seeing for a long time — a fired-up Democratic base.”

Romney pollster Neil Newhouse dismisses the idea that enthusiasm will be a problem. “We’re confident that on Election Day Republicans are not only going to be solidly, overwhelmingly behind Mitt Romney but will be voting for him with enthusiasm over Barack Obama,” he says.

The president faces a more serious issue, Newhouse says: Lagging ratings on managing the economy, the issue both campaigns predict will dominate the campaign.

Among those surveyed, 60% say a President Romney would do a good or very good job handling the economy over the next four years; 52% say that of Obama. Even among the president’s supporters, four in 10 predict Romney would do a good job. In a direct comparison, Romney edges Obama, 47%-44%, as the one who would do a better job.

“You’ve got a candidate who has just been through the bruising Republican primary and came out somewhat bloodied, so it’s pretty remarkable that in these target states Gov. Romney is doing better than Obama on the biggest issue, the economy,” Newhouse said. “It’s hard to read it any differently than a public indictment of the president’s economic policy.”

The up-for-grabs states surveyed are Colorado, Florida, Iowa, Michigan, Nevada, New Hampshire, New Mexico,North Carolina, Ohio, Pennsylvania, Virginia and Wisconsin.

The economy is the issue for Bill Alvey, 55, a software developer from Colorado Springs, as he considers whom to support. He was among those polled.

“At this point, I would say Mitt Romney, assuming that nothing monumental happens between now and then,” Alvey said in a follow-up interview. “I realize Obama didn’t inherit a wonderful economic situation, but it just seems the last four years, it’s like — are you better off than you were four years ago? As a country, I just feel like we are much worse off than we were four years ago.”

Who’s more likable?

Obama has some advantages.

By a yawning 27 points, those surveyed describe Obama as more likable than Romney — not a frivolous asset. The candidate viewed as more likable has prevailed in every election since 1980. Even among Romney’s supporters, one in four call Obama more likable.

By 10 points, voters say Obama is more likely to care about the needs of people like themselves. By 7 points, they call Obama a stronger and more decisive leader.

“No president can get everything done in four years,” says LaTonya McCants, 44, a nursing assistant from Cleveland and an enthusiastic Obama backer. “He did make some good changes, and I feel he should get another four years” to finish the job.

Times may be tough, but she believes Obama is on her side. “He’s for everybody,” McCants says. Who does Romney care about? “Probably the business people,” she says.

Romney is seen as equally capable of managing the government, leading Obama by 2 points on that trait.

The bottom line: Voters already have clear and distinctly different perceptions of the two candidates — their skills, personalities and political views — even though many of them are only beginning to pay attention to the presidential race.

“Obama has the softer image dimensions tied up: He’s likable, compassionate, feels your pain, relates, understands,” says Frank Newport, Gallup’s editor in chief. “These are presumably the dimensions that appeal to today’s Democratic coalition,” which includes most non-white and younger voters as well as some highly educated whites.

Voters see Romney as an “efficient manager” to handle the economy with “a more Darwinian approach,” Newport says. “He’s less interested in feeling your pain than telling you how to fix your pain by … doing something about it.”

Consider how the candidates were campaigning almost precisely six months before Election Day on Nov. 6. Obama officially launched his campaign Saturday at huge rallies on college campuses in two of the swing states, Ohio and Virginia. Romney spent time last week in theOld Dominion, too, decrying the president’s economic policies to supporters gathered at small businesses.

On a political spectrum

When it comes to ideology, perceptions also are set.

About a third of voters say Obama’s political views and their own are about the same while a 54% majority say the president is more liberal than they are. Just one in 10 say he’s more conservative.

About a third of voters say Romney’s political views and their own are about the same, and he’s seen as roughly in the middle of the political spectrum: About one in three call him more conservative than they are; about one in four call him more liberal.

Seven of 10 voters in those states say their minds are firmly made up and won’t change. Both campaigns are focused not only on firing up enthusiasm among those core supporters but also winning over the 7% who are undecided and the 24% who are only loosely committed to a candidate.

Under the United States’ unique Electoral College system, that fraction of voters in a dozen states are likely to decide who can claim the presidency for the next four years. Based on turnout in 2008, these swing voters in the swing states consist of roughly a million people in Virginia; 1.6 million in Ohio; 2.5 million in Florida; 220,000 in New Hampshire — a total of about 13 million voters out of an expected national turnout of more than 130 million.

The next six months, when political spending will likely top $2 billion, will be aimed in large part at winning them over.

In the 2008 campaign, almost precisely the same proportion of voters were up for grabs until late August, when it began to decline sharply with the choice of a Republican vice presidential candidate and the political conventions. By Election Day, the number of uncommitted voters nearly disappeared.

Who are these persuadable voters?

This time, they tend to be Republican or Republican-leaning. Half describe themselves as moderate; six in 10 say Obama is more liberal than they are. They give the president a lower job-approval rating (40%) than other voters. By 2-to-1, they predict Romney would do a better job in handling the economy.

Even so, they aren’t solidly on Romney’s side, at least not yet.

Katherine O’Leary, 25, of Hillman, Mich., isn’t sure whether she supports Romney but she knows she opposes Obama. “I think he’s an amateur and he doesn’t know what he’s doing,” she says. But she’s leery of Romney, in part because of the health care bill he signed into law in Massachusetts.

“It’s a mini-version of the (federal) health care law, more of a big-government thing,” says O’Leary, who was called in the poll. In the primaries, her preferred candidate was former business CEO Herman Cain. “He seemed honest and it was like he knew what he was doing,” she says. “He had a plan.”

For Romney, winning swing voters will require making his case and a personal connection, even if Obama continues to be seen as the more likable candidate. Newhouse notes that the president’s advantage on that characteristic hasn’t translated into a clear lead so far. “They’re going for competence over likability,” he says of voters.

For Obama, it means strengthening his hand on economic issues — an effort linked to how the economy fares — and countering Romney’s appeal. “I think the more people examine Gov. Romney’s record, the less likely they are to believe he’s a credible messenger on the economy,” Messina says, citing a “record of off-shoring jobs overseas as governor and as a corporate buyout specialist.”

Jamie Richardson, 41, of Altoona, Pa., is a swing-state voter who hasn’t made up his mind.

On one hand, he owes Obama a personal favor. Soon after the inauguration in 2009, his wife, who is German, wrote the president a letter explaining that she was having trouble negotiating the system to get a green card. Within days, she got a response and the problem was unraveled.

“He’s done a good job for us there,” says Richardson, an Army veteran of Desert Stormwho now works at Wal-Mart. On the other hand, he says, “Looking at it overall … I don’t like what he’s done while he’s in office,” and he’d like to learn more about Romney.

He has some advice for both candidates.

“Every president, they make promises and promises,” he says. “The thing that irritates me, they say, ‘I’m going to do this in office.’ Well, you can’t say that. You have the Congress to get it through. … Be honest. Say, ‘I will try to do this.’”

The candidate who does that, he says, is likely to get his vote.