By JULIA PRESTON and FERNANDA SANTOS
Defying predictions that their participation would be lackluster, Latinos turned out in record numbers on Tuesday and voted for President Obama by broad margins, tipping the balance in at least three swing states and securing their position as an organized force in American politics with the power to move national elections.
Over all, according to exit polls not yet finalized by Edison Research, Mr. Obama won 71 percent of the Hispanic vote while Mitt Romney won 27 percent. The gap of 44 percentage points was even greater than Mr. Obama’s 36-point advantage over John McCain in 2008.
After waiting in long lines in countless places — more than four hours at some South Florida polls — Latinos had such a strong turnout that it lifted them to 10 percent of voters nationwide, an increase from 6 percent in 2000. Latino leaders said their voters had cast ballots that ensured Mr. Obama’s relatively narrow plurality — fewer than 2.8 million votes — in the popular count.
“Latino voters confirmed unequivocally that the road to the White House passes through Latino neighborhoods,” said Clarissa Martinez De Castro, a top official at NCLR, the Hispanic organization also known as the National Council of La Raza, which joined in an extensive campaign this year to register and turn out voters.
Latinos’ greatest impact was in several battleground states portrayed by polls as close contests before Election Day. In Colorado, Nevada and New Mexico, Mr. Obama won the Hispanic vote by big percentages that well exceeded margins of victory, exit polls showed. In each of those states, Latinos significantly increased their share of total voters, gaining influence that could be decisive in future elections.
In Florida, where Mr. Obama held a narrow lead on Wednesday in a race that had not yet been called, the president won among Latinos by 60 percent to 39 percent for Mr. Romney, among a group that now makes up 17 percent of the state’s voters.
Mr. Romney’s weak showing prompted Latino leaders to warn that Republicans could no longer afford to ignore or alienate Hispanics in national races. But they also immediately laid out an ambitious agenda for Mr. Obama, saying they expected to see jobs programs tailored to Latinos and quick action on legislation to give legal status to millions of illegal immigrants.
“The sleeping Latino giant is wide-awake and it’s cranky,” said Eliseo Medina, international secretary-treasurer of the Service Employees International Union, another group that played a central role in spurring Latinos to vote. “We expect action and leadership on immigration reform in 2013. No more excuses. No more obstruction or gridlock.”
In many states, Latinos did not wait for either the Democratic or the Republican campaigns to come to them. Instead they mounted coordinated voter registration and education efforts, giving them a degree of independence as a voting bloc and creating popular networks that they said they planned to mobilize again to bring pressure on the White House and Congress.
In Arizona, a conservative state known for tough immigration enforcement policies that Mr. Romney won handily, Latinos saw setbacks. A bid to unseat Joe Arpaio, the hard-line sheriff of Maricopa County, was declared to have failed. A Hispanic Democrat, Richard Carmona, apparently was defeated in a Senate race by Jeff Flake, a popular Republican who has served in the House of Representatives.
Records from the office of Secretary of State Ken Bennett showed Wednesday that there were 600,000 votes yet to be counted statewide.
Luis Heredia, the executive director of the Arizona Democratic Party, said the outcome of many close races could not be determined without the counting of those ballots.
A crucial piece of Mr. Obama’s winning strategy among Latinos was an initiative he announced in June to grant temporary reprieves from deportation to hundreds of thousands of young immigrants here illegally. In a survey of 5,600 Latino voters on the eve of the election by ImpreMedia and Latino Decisions, a polling group, 58 percent said the reprieves had made them “more enthusiastic” about Mr. Obama.
Last month, Mr. Romney said that he would end the reprieves if he became president, a move that solidified the view among many Latinos that he was hostile to a program they liked. It gives young immigrants protection from deportation for two years and also work permits that allow them to be employed legally in this country for the first time.
A campaign led by young immigrants eligible for the deferrals was one of the most effective voter mobilization efforts.
“Even though we could not vote, we had many friends and family members who could,” said Lorella Praeli, advocacy director of the United We Dream network, a youth group that led a voter campaign.
In Arizona, a dozen groups teamed up to increase Latino voter registration and to add more Latinos to the state’s early-voting list, which entitles voters to receive ballots by mail at their homes. The number of Latinos on early-voting lists rose substantially, to 225,000 this year from 96,000 in 2008, said Petra Falcón, director of Promise Arizona, one of the groups in that effort.
On Tuesday, the groups dispatched monitors to poll sites where they knew many Latino voters would be casting ballots for the first time.
By midmorning, it had become clear that a lot of them were being forced to cast provisional ballots because officials could not find their names on the rolls. In a precinct in Tolleson, 300 out of 342 votes cast by 4 p.m. were provisional ballots, according to poll monitors assigned to the site. At Word of Abundant Life Christian Center in West Phoenix, 68 out of 123 voters had used provisional ballots by that hour.
Adilene Montesinos, a poll worker at Progressive Baptist Church in Mesa, said the problem had affected Latinos and also blacks. “There were so many, we almost ran out of provisional ballots,” Ms. Montesinos said.
Officials in Maricopa County, which accounts for more than half of the state’s voters, said the count of provisional ballots was not likely to begin until Monday. The officials said Wednesday that 344,000 ballots remained to be counted, among them 115,000 provisional ballots.