Both candidates were backed by legions of surrogate campaigners, door to door canvassers and volunteers at phone banks scattered across the country as they made their final rounds Saturday in a race that carried a price tag estimated at $2 billion.
Obama, ahead in the polls, maintained stride despite news that an aunt from Kenya, Zeituni Onyango, lives in the U.S. illegally. The Democratic candidate "has no knowledge of her status but obviously believes that any and all appropriate laws be followed," said a written statement given to The Associated Press, which reported the story.
Campaign strategist David Axelrod added, "I think people are suspicious about stories that surface in the last 72 hours of a national campaign."
McCain made no mention of Obama's relative, but he worried aloud about the consequences of Democrats winning the White House while maintaining control of Congress. He warned of an agenda that "apparently ... starts with lowering our defenses and raising our taxes."
He contended that Obama was "running for redistributor in chief, I'm running for commander in chief."
The Republican spent much of the day in Virginia, trying to make up ground in a state that has not voted Democratic since 1964 but leans that way now. "We're a few points down, but we're coming back," he said. "I'm not afraid of the fight, I'm ready for it and you're going to fight with me."
Obama was in Nevada, then Colorado and Missouri, all states that voted for President Bush four years ago. Obama's visit to Colorado marked his sixth trip to the swing state since he clinched his party's nomination in June.
"We have a righteous wind at our back," he told one audience. When Obama arrived in Pueblo, Colo., his family was waiting for him on the tarmac, wife Michelle and daughters Malia and Sasha. Obama kissed his wife, hugged his daughters.
"We are three days away from bringing fundamental change to the United States of America," Obama said. He told the crowd not to let up. "Not when so much is at stake," he said. "We've got to win Colorado, and we're going to win this election."
Obama, bidding to become the nation's first black president, led in national polls as well as surveys in several battleground states. McCain's hopes of an upset hinged on winning all or nearly all the states that carried Bush to victory in 2004, and possibly carrying Pennsylvania to give him a margin for error.
Apart from the presidential campaign, Democrats confidently predicted they would add to their majorities in the House and Senate.
Senate Republican leader Mitch McConnell of Kentucky was in a close and costly battle for re-election.
But so was Democratic Rep. John Murtha, several days after describing his southwestern Pennsylvania constituents as racists. Democrats arranged for former President Clinton to campaign for the anti-war lawmaker in hopes of saving his seat.
Bush was nowhere near the campaign crowds as the election neared, and McCain wouldn't have it any other way, given low presidential approval ratings.
But Vice President Dick Cheney went home to Wyoming, where Democrats were making a spirited bid for the state's single House seat. "Our country cannot afford the high tax liberalism of Barack Obama and Joe Biden," he said.
The Democrats jumped on that.
Obama seized on Cheney's fresh endorsement of McCain, praising the vice president for climbing out of his "undisclosed location."
"I'd like to congratulate Sen. McCain on this endorsement, because he really earned it," Obama said in Pueblo, Colo. "That endorsement didn't come easy. Sen. McCain had to vote with George Bush 90 percent of the time and agree with Dick Cheney to get it." Like Obama and McCain, the vice presidential running mates campaigned toward the finish line.
Sen. Joe Biden was in Indiana, another traditionally Republican state where Democrats are running hard, and later in Ohio, a competitive state. He accused Republicans of "trying to take the low road to the highest office in the land. They are calling Barack Obama every name in the book."
Republican Sarah Palin, in New Port Richey, Fla., said Biden had it backwards - it was the Democrats who were resorting to unseemly tactics.
"Barack Obama goes around promising a new kind of politics, then he comes here to Florida and tries to exploit the fears and worries about Social Security and Medicare for retirees, and that's the oldest and cheapest kind of politics there is," she said. Palin said in Raleigh, N.C., later that Obama's tax plan will dash the dreams of Americans and their children as she urged voters in this surprise swing state to vote against such a change.
"If you believe America is still the land of possibilities and if you don't want your dreams dashed and your children's dreams dashed by the Obama tax increase, then, North Carolina, we're asking for your votes," Palin told several thousand at the state fairgrounds in Raleigh.
The rhetorical flourishes were merely the most visible aspect of the late-campaign effort.
McCain's campaign said it was reaching more voters than Bush's re-election campaign did at this point four years ago, more than one million a day. Volunteers in reliably Republican states like Utah were bused to nearby battlegrounds like Nevada.
Democrats had a similar plan. Volunteers in Maryland were told they were needed in Virginia.
Early voting statistics were large, and tilted Democratic. In North Carolina, officials said 2.3 million ballots had been cast as of Saturday morning, 52 percent of them by Democrats and 30 percent by Republicans.
In Missouri, spokesman Justin Hamilton said Obama's campaign had agreements with cab companies across the state to provide Election Day rides to the polls for any voter who wanted one.
He said the callers would not be asked how they intended to vote.
David Espo reported from Washington. AP's Ben Feller contributed from Pueblo, Colo., Nedra Pickler from Chicago, Rodrique Ngowi and Jay Lindsay from Boston, Mike Baker in Raleigh, N.C., Mike Smith in Evansville, Ind., and Joan Lowy and Liz Sidoti from Washington.