Sens. John McCain and Barack Obama kept campaigning right through Election Day, although scenes from crowded polling places today indicated that voters did not need any last-minute encouragement.
Across the country voters are turning out in what could be historic numbers, in some cases spending hours in serpentine lines waiting for a chance to vote.
In an indication of how intensely fought this campaign has been, both candidates kept holding large rallies and television interviews even as voters swarmed to their polling sites. In the past, presidential candidates have halted their campaigns on Election Day.
McCain voted early in Phoenix before heading off for some last-minute get-out-the-vote efforts in New Mexico and Colorado, two states where the GOP presidential pick is trailing but hopes to pull out narrow victories.
"I promise you if I'm elected president, I will never let you down," an energized McCain told a crowd in Colorado.
"I think we ought to hear one more time 'drill, baby drill,'" he cheerfully suggested and the crowd obliged with the campaign's chant.
In the battleground state of Pennsylvania, where McCain is trailing, the Republican National Convention placed robocalls using quotes from Sen. Hillary Clinton criticizing Obama. The GOP in Pennsylvania is running ads reminding voters of Obama's relationship with his former controversial minister, the Rev. Jeremiah Wright.
After voting at a Chicago school, Obama spent the morning campaigning in Indiana before returning to Chicago to conduct television interviews broadcast via satellite to the swing states of Florida, Pennsylvania, Colorado, Virginia, Ohio, North Carolina, Nevada and Missouri.
Lines at polling stations around the country indicate the election could result in record turnout numbers.
Kim Wooten, 44, waited in line for 75 minutes to vote at a fire station in Rosslyn, Va., and said she would cast her vote for Obama.
"I'm ready for a change," she said. "To be honest, I wasn't really energized about either candidate, but I'm voting Democratic this time."
Wooten was one of thousands voting in Virginia, long considered a Republican stronghold but which has been leaning toward Obama in the polls.
Polls in the state close at 7 p.m. ET, one of the earliest closing times in the country, and could, according to Democratic vice presidential nominee Joe Biden indicate the direction of results throughout the night.
"The polls are going to close and by 9 ET -- you will have Virginia, North Carolina, Pennsylvania, Ohio, by that time. ... You're going to know whether you're going to be up a long, ... long night or if it's going to be a short night," Biden said.
Obama, who could become the nation's first black president, voted with his two young daughters in Chicago before he plunged into a final round of campaigning in Indiana.
"I voted," the Democratic presidential candidate said, holding up the validation slip he was given after turning in a ballot at the Shoesmith School in his Chicago neighborhood.
Obama voted at the same polling station as William Ayers, the former 1960s radical who became a flashpoint in the campaign when the McCain campaign accused Obama of "palling around" with terrorists.
Nation of Islam leader Louis Farrakhan also voted at that site. Farrakhan became a GOP target after he endorsed Obama.
In Delaware, Biden, Obama's running mate, went to the polls with his mother before getting on a plane to meet up with Obama in Chicago.
Sarah Palin, McCain's running mate, arrived in Anchorage, Alaska, overnight and voted in her hometown of Wasilla. She is expected to fly to Phoenix to join McCain in time to watch the results come in.
After voting, Palin noted that the result would be historic, implying that the voters would elect either the country's first black president or the first female vice president.
"It bodes so well the progress our country is making," Palin said.
She also said she was delighted that she was cleared of any wrongdoing in the firing Alaska's top police officer.
"You didn't believe us," she told reporters. "I told you we'd done nothing wrong."
In Florida, a swing state marginally leaning Republican, voters in some cities were confronted with long lines, while others found shorter queues in areas that had high early voter turnout. By some estimates nearly 50 percent of Florida's likely voters had cast absentee or early ballots.
"If Obama gets elected, I'll definitely go back [to Iraq] because they are going to test him," said a 40-year-old Air Force colonel who voted Republican in Sarasota, Fla., and asked that his name not be used. "Obama's done nothing except get endorsed by Oprah. McCain will bring troops home in an orderly fashion."
Today's vote caps a long-fought and record-breaking campaign between two candidates who were both written off early in their candidacies and whose races for the White House have been nothing short of history making.
"The election is historic by any standard. Barack Obama might become the first African-American president. One woman, Hillary Clinton ran and nearly secured her party's nomination; another, Sarah Palin, could potentially be the first female vice president," said Matthew Dowd, an ABC News political consultant. "We're seeing a great generational shift."
By almost every quantifiable measure -- from the $640 million Obama raised in the month of October, to the nearly $1 billion combined the campaigns have spent, to 9 million newly registered voters -- records have been shattered.
Yet another record may fall before the day is over as turnout is heavy and could surpass previous voting turnout records. The existing turnout records were set in 2004 when more than 122 million Americans went to the polls, and in 1960 when 64 percent of eligible voters cast a ballot.
All eyes are now on a handful of battleground states that can turn the election or signal a sea change in American politics.
While McCain faces a tough road to the necessary 270 electoral votes, victories in tightly contested Florida, Ohio and Virginia could significantly shift the electoral map in his favor and result a win.
Polls close earliest in Virginia -- at 7 p.m. ET -- and in Indiana, some polls close at 6 p.m. ET (that's 7 p.m. ET).
"The first thing to look at is Virginia," said Dowd. "If Obama has the lead there, you know the outcome of the race. If McCain wins or it's too close to call, anything can happen."
The election comes in the midst of the worst economic crisis since the Great Depression, and at a time when 85 percent of the populace believes America is on the wrong track.
The candidates have spent almost two years staking their positions on a broad swath of issues, but in the lead-up to Election Day, voters said the economy trumped everything
Obama retained an overall lead in the most recent ABC News/Washington Post poll, 54 percent to 43 percent, among likely voters interviewed Wednesday through Saturday.
The candidates' identities, as much as where they stand on issues, have been a mainstay of the campaign. McCain, a bona fide war hero and long-serving lawmaker, would be the oldest first-term president if elected. Obama, a virtually unknown Illinois junior senator when he announced his candidacy, will be the first black president if he wins.
Since Obama was pitted against former first lady Sen. Hillary Clinton of New York during the Democratic primaries, America's best principles and worst prejudices have been confronted and debated.
Sexism became an issue, first when Clinton argued that sexist treatment in the media and electorate had scuttled her chances at the nomination, and more recently when Palin complained that focus on her $150,000 GOP-bought wardrobe would not have been an issue if she were a man.
McCain goes into today's voting a decided underdog trailing in the polls. But with a flailing economy and an unpopular Republican president, some have argued that the deck is stacked against him, or any Republican nominee.
"People are looking for great meaning and significance in this election. Given the state of economy, I don't think it's a surprise that Obama is leading," said ABC News political consultant Torie Clarke, a former assistant secretary of defense during the first term of the Bush administration.
Obama did more than just tap into growing feelings of resentment. He offered a candidacy centered around hope and optimism, and, in perhaps the greatest and most calculated flip-flop of his campaign, forwent public financing allowing him to raise hundreds of millions of dollars from donors contributing small amounts of money.
McCain too changed course. In the final weeks of the campaign, the Arizona senator struck a more negative tone and along with Palin began attacking Obama on his relationships and judgment.
In the third and final presidential debate, McCain assailed Obama for his relationship with 1960s radical William Ayers and his campaign began aggressively using auto-dialed calls to voters, known as "robocalls," to relay negative messages, frequently focusing on the Democrat's experience and readiness for the White House.
That strategy didn't seem to achieve the desired effect, with voters responding in polls in the race's final weeks that they were turned off by the negative ads and attack tactics.
Obama has in recent weeks consistently led in national polls and the electoral math as it stands clearly favors him. Buoyed by newly registered voters, blacks and young people, Obama has found support even in states once considered Republican strongholds. But things are far from absolute and both supporters and opponents of Obama note that anything can happen.
Mosheh Gains contributed to this report from Virginia and Ellen McKeefe from Florida.