But will this enthusiasm -- which propelled his victory Tuesday in the race for the Democratic nomination -- deliver enough of these states to Obama to win the presidency?
McCain, for his part, must hold all of Bush's states, or else carry some new ones to make up for any losses.
"Everybody's top priorities will be those 12 to 15 swing states that were close in 2004," said Charles Black, a senior McCain advisor.
For weeks, Obama and McCain have crossed paths in those states, with a particular emphasis on Florida. When South Dakota and Montana handed Obama the delegates needed to clinch the nomination Tuesday night, he did not celebrate in either state, but in Minnesota -- a state that is crucial for Democrats to hold.
Obama is running in a climate that strongly favors Democrats. Advisors say he is well-placed to expand the map of Democratic states to Colorado and Virginia, a pair of Bush states now more friendly to his party -- and might even add such GOP strongholds as Georgia.
Yet a wholesale recoloring of the nation's red-and-blue electoral map is hard to fathom, strategists and independent analysts say.
Instead, the Illinois senator probably will battle McCain most fiercely in states around the Great Lakes and in the Southwest -- those with the narrowest vote margins between Bush and his 2004 Democratic challenger, Massachusetts Sen. John F. Kerry.
McCain stands a plausible chance of carrying perhaps half a dozen states that Kerry won. The Arizona senator's popularity with independents puts states such as Wisconsin and New Hampshire within reach.
Two other states that went Democratic in the last presidential contest -- Pennsylvania and Michigan -- are also top McCain targets, thanks partly to Obama's trouble bonding with working-class white voters.
But, pollsters say, McCain's standing has been inflated by the protracted Democratic nomination fight. Now that the attacks on Obama by rival Hillary Rodham Clinton will recede into the past, they say, McCain's poll numbers are likely to drop.
"He'll have the challenge of beating a solidified Democratic Party, and that's going to be a tough row to hoe," said Frank Newport, editor in chief of the Gallup Poll.
McCain's campaign has put forward optimistic election-day scenarios, saying he can pick up Democratic-leaning states such as New Jersey and Washington.
But once Democrats unite, the dismal environment for Republicans could force him to devote more effort to defending states that Bush won. The sluggish economy, the Iraq war and Bush's unpopularity are potentially major drags on McCain's candidacy, even if his iconoclastic image gives him some distance from his beleaguered party.
"The concept that McCain is going to put the Pennsylvanias of the world in play is a much less plausible scenario than the Democrats putting the Missouris and Ohios in play," said Ruy Teixeira, co- author of "The Emerging Democratic Majority."
Obama's team has laid out its best-case scenarios
. "We feel we can stretch the battlefield," Obama strategist David Axelrod said.
In Georgia and Virginia, about 700,000 African Americans who are eligible to vote are not registered, and Obama has the money and volunteer force to sign them up, said Steve Hildebrand, his deputy campaign manager.
But apart from Virginia, where the rapidly growing Washington suburbs have fueled recent Democratic victories, the South looks bleak for Obama, pollsters say. Recent Democratic wins in Mississippi and Louisiana congressional races have sparked new hope for Obama, but pollsters say that black voters who drove his victories in Southern primaries are unlikely to be numerous enough to overcome the region's strong GOP leanings.
"The truth is there is no relationship . . . between how you do in a primary election in a state and how you do in a general in that state," Democratic pollster Mark Mellman said.
In the Southwest, McCain holds an edge in Arizona, his home state. But in Colorado, Nevada and New Mexico, rapid population growth -- and an influx of Latinos -- has led to newly favorable conditions for Democrats.
Bush, who drew 45% of the Latino vote in 2004, carried the three states. McCain hopes that his support for legalizing many undocumented immigrants, and the political price he paid for it within his party, will keep him competitive with Latinos. Also comforting to McCain: Latinos have sided with Clinton over Obama in Democratic contests, most recently on Sunday in the Puerto Rico primary.
For Obama, perhaps the biggest challenge lies in three big industrial states that offer a rich trove of electoral votes: Ohio, Pennsylvania and Michigan.
In the Ohio and Pennsylvania primaries, Obama won scant support from white blue-collar voters, a key bloc in the Rust Belt. History suggests that they will lean toward McCain. In 2004, white voters with no college degree voted for Bush over Kerry by 23 percentage points; Obama cannot afford to lose them by such a wide margin.
McCain's support of free trade, especially the North American Free Trade Agreement, could hurt his effort in the economically pressed region. But "there's going to be some natural appeal for the old war veteran who sort of speaks his mind," said William Frey, a senior fellow at the Brookings Institution.
Frey described Obama as "a harder person for a lot of these older, middle-aged baby boomers and seniors to identify with."
As the first black presidential nominee of a major party, Obama will also face a race factor. "I wouldn't say it's out and out racism," Frey said, "but it's the whole idea of changing from the stereotypical candidate they're used to."
At the same time, a surge in black turnout in Cleveland, Cincinnati, Philadelphia, Detroit and other cities could offset any Obama shortfall among working-class whites.
In the Midwest and elsewhere, Obama and McCain face a highly competitive campaign for independents, notably in Minnesota and Wisconsin, states that Kerry won by narrow margins.
"The fact that neither one of them is seen as a tough, hard-core partisan gives them both entree to those voters that other nominees in the past haven't had," said Democratic strategist Bill Carrick.
One state Bush won in 2004 is particularly ripe for Obama to pick up: Iowa. Obama built a powerful organization that swept him to victory in Iowa's Democratic caucuses in January.
But Florida, a far more populous swing state and the scene of the 2000 vote-count debacle, could be tough for Obama. Older voters, a vast group there, strongly preferred Clinton over Obama. And Obama has struggled to gain the trust of some Jewish voters, a crucial constituency in South Florida. That dynamic has led to fierce competition between Obama and McCain over which would be a stronger champion of Israel's security.