McCain and Barack Obama began their final push for the White House on Saturday across an electoral map markedly different from four years ago, evidence of Mr. Obama's success at putting new states into contention and limiting Mr. McCain's options in the final hours. Mr. Obama was using the last days of the contest to make incursions into Republican territory, campaigning Saturday in three states " Colorado, Missouri and Nevada " that President Bush won relatively comfortably in 2004. In what seemed as much a symbolic tweak as a real challenge, Mr. Obama bought advertising time in Arizona, Mr. McCain's home state. Mr. McCain started the day in Virginia, a once-solidly Republican state that Democrats now feel is within their grasp. But he then turned his attention to two states that voted Democratic in 2004 " Pennsylvania and New Hampshire " reflecting what his aides said was polling in both states that suggested the race was tightening. Still, his decision to spend some of his time in the final hours on Democratic turf signaled that Mr. McCain had concluded that his chances of winning with the same lineup of states that put Mr. Bush into the White House was diminishing. Mr. McCain's hopes appear to rest in large part on his ability to pick up electoral votes from states that Senator John Kerry won for the Democrats four years ago. Across the country, there was abundant evidence of just how much excitement the contest had stirred: In Colorado, 46 percent of the electorate has already voted in that state's early voting program. Voters in states like Missouri, Montana, North Carolina and Virginia were getting knocks on their doors, telephone calls and leaflets slipped under their windshield wipers. And Mr. Obama and Mr. McCain used their last hours on the public stage to return to the themes that have marked their candidacies.  "After 12 months and three debates," Mr. Obama said in Henderson, Nev., "John McCain has not been able to tell the American people a single major thing that he would do different from George Bush on the economy." Mr. McCain warned that an Obama presidency, combined with a Democratic Congress, would lead to higher taxes. "Presidential elections have a way of settling on a few great questions as the moment of decision arrives," Mr. McCain said in a radio address. "And this has happened in the closing days of the election of 2008. We've learned that Barack Obama's economic plan for America is to redistribute the wealth of America with higher taxes." At a rally in central Florida for Mr. McCain's running mate, Gov. Sarah Palin, supporters chanted "John McCain Not Hussein" Mr. Obama's middle name is Hussein, and some of his opponents use it to falsely suggest that he is Muslim. The campaign's final days brought a reminder of how Mr. Obama's financial might had allowed him to redraw the political map. In addition to the states he visited on Saturday, Mr. Obama was planning stops Sunday in Florida, North Carolina and Virginia, which went Republican four years ago. His campaign manager, David Plouffe, said the campaign was confident of holding onto New Hampshire and Pennsylvania. "All the Kerry states right now are in good shape for us," he said. Mr. McCain and his advisers said they saw evidence they were gaining on Mr. Obama as Mr. McCain hammered away at his message that Mr. Obama would raise taxes. "We have never been as convinced as others by some of the discouraging numbers," said Nicolle Wallace, a senior McCain adviser, adding, "We are certainly encouraged by the tightening of the polls." But the bulk of his last-minute campaign spending and appearances by Mr. McCain and Ms. Palin were in places like Florida, North Carolina and Virginia. "If the race were closer, the states he'd be going to would be blue states," said Matthew Dowd, chief strategist to Mr. Bush in 2004. "He's campaigning as if he knows he's significantly behind."Tad Devine, who was senior adviser to Mr. Kerry, said Mr. Obama was in a substantially stronger position than Mr. Kerry was.