Whoever won Colorado under this set of circumstances would become president.
At the moment, "it's really sort of neck and neck," says Floyd Ciruli, an independent pollster in Denver.
Republicans carried Colorado in every presidential election over the past 40 years, except 1992. But the state is realigning.
Democrats have taken control of the legislature and in 2006 captured the governorship and a U.S. Senate seat.
The new senator, Ken Salazar, became the chamber's first Hispanic Democrat in decades, a sign of the growing political power of the state's expanding Latino population. Affluent liberals are moving in from places like California, and Democrats have cut a 175,000-vote Republican registration advantage by more than half in recent years.
To highlight the shift, Democrats staged their national convention in Denver, and Obama's acceptance speech extravaganza at Mile High stadium was designed in part, aides said, to recruit thousands more grass-roots volunteers in the state.
McCain answered with Palin, an Idaho native who appears to be connecting with the region's voters.
"She's a gun-totin' Westerner. She's a frontier girl, and we have a lot of identification with the frontier," said Ciruli. "If she can capitalize on that, she might be a new influence in the race."
Republicans say Palin has already changed the mind-set in Colorado, a state McCain lost to Mitt Romney during primary season. Back then, evangelical Christian leader James C. Dobson declared that "I cannot, and I will not vote for Sen. John McCain, as a matter of conscience." When Palin joined the ticket, Dobson endorsed McCain.
Dick Wadhams, a veteran campaign strategist who chairs the state Republican Party, said there was "an enthusiasm lag" among social and cultural conservatives that's been "totally obliterated by the addition of Palin."
Among Colorado Republicans, there's a new attitude of "we can win this thing," he said. "I think the Democrats were a little bit cocky and arrogant for their own good" about their chances.
Last weekend, fresh from the Republican convention, McCain and Palin starred at a large rally in Colorado Springs, which is Dobson's home base. This weekend, Palin is back in the state again.
Obama returns tomorrow, with events in Pueblo, a working-class city with a large Hispanic population, and in Grand Junction on the Western Slope.
