"My friends, it's official: There's just one day left until we take America in a new direction," McCain said at a raucous, heavily Hispanic rally in Miami just after midnight.
The candidates' disparate schedules on the last day of the long presidential contest reflected the overall state of the race going into its final hours.
Obama, cruising comfortably ahead in national and many battleground state polls, was starting his day with a late morning rally in Jacksonville, before heading to events in Virginia and North Carolina.
McCain, meanwhile, was struggling to hang onto those and other states that voted for President Bush in 2004 in hopes of preserving a slim path to victory Tuesday night.
The Arizona senator planned a demanding schedule across time zones, beginning early in Tampa and going on to Tennessee, whose media market reaches into Virginia. He was also scheduled to hit Pennsylvania, Indiana, New Mexico and Nevada before ending early Tuesday with a rally in Prescott, Ariz., before returning home to Phoenix.
McCain's running mate, Sarah Palin, was racing through five Bush states - Ohio, Missouri, Iowa, Colorado and Nevada - in an effort to boost conservative turnout. The Alaska governor has been a popular draw for many GOP base voters.
Joe Biden, Obama's running mate, was to campaign in Missouri, Ohio and Pennsylvania.
Polls show the six closest states are Florida, Indiana, Missouri, North Carolina, Nevada and Ohio. The campaigns also are running aggressive ground games elsewhere, including Iowa, New Mexico, Pennsylvania, New Hampshire, Colorado and Virginia.
Breaking with tradition, both candidates planned to campaign on Election Day. McCain scheduled campaign stops in Colorado and New Mexico while Obama was set to make a quick trip to Indiana before returning to Chicago for a massive rally in Grant Park.
Obama exuded confidence Sunday at events in three cities in the bellwether state of Ohio, which voted for President Bush in 2000 and 2004 but is trending Democratic this year as it struggles against an anemic economy.
"We cannot afford to slow down or sit back or let up," Obama told voters at an evening rally in Cincinnati. "We need to win an election on Tuesday."
An e-mail to Obama's Ohio supporters signed by former Vice President Al Gore reminded them that the state was decided by an average of nine voters per precinct in 2004. Gore asked for volunteers in the final two days to keep Obama from losing the state.
McCain was fighting to hold onto Florida's 27 electoral votes while making a play for Pennsylvania and New Hampshire, two states that voted for Democrat John Kerry last time but which McCain's advisers believe could swing to the GOP this year. Polls, however, show Obama comfortably ahead in both places.
In New Hampshire, McCain held his last town hall meeting of the 2008 campaign - something of an exercise in nostalgia, as he conducted dozens of such freewheeling affairs in the months leading up to his victory in that state's primary.
McCain took voter questions on issues like illegal immigration and paying for college while thanking New Hampshire for rescuing his campaign in 2008 and in the 2000 Republican primary, when he briefly upended George W. Bush.
"I come to the people of New Hampshire to ask them to let me go on one more mission," McCain said in Peterborough, where he was introduced by Boston Red Sox pitcher Curt Schilling.
In Pennsylvania, the Republican National Committee placed automatic telephone calls, or robocalls, using quotes from Obama's Democratic rival Hillary Rodham Clinton where she criticized Obama during last year's primary season. The New York senator repudiated the calls in a statement.
The Pennsylvania Republican Party was running ads reminding voters of Obama's relationship with his incendiary former pastor, the Rev. Jeremiah Wright. Obama severed ties with Wright after videotapes surfaced showing the pastor making anti-American statements from the pulpit of Chicago's Trinity United Church of Christ, where Obama worshipped for 20 years.
McCain has refused to make Wright a campaign issue but the Pennsylvania GOP said it spoke to Obama's character and judgment.
"Do we want the next President of the United States to have spent years listening to hateful rhetoric without having the good judgment to walk out?" the committee said in a statement on its Web site.
Associated Press writer Nedra Pickler contributed to this report from Cincinnati.