Polls show Obama winning the broadest support from Latino voters of any Democrat in a decade, while McCain is struggling to reach 30 percent, closer to Senator Bob Dole's dismal 1996 result than to Bush's historic 40% four years ago.
McCain seems to have wound up with the worst of both worlds: He appears to be getting no credit from Latino voters for his past support for immigration reform, while carrying the baggage of other Republicans' hostility to illegal immigration.
And he's been unable or unwilling to attack Obama—who was once thought to have taken a lethally liberal stance by supporting granting drivers licenses to illegal immigrants—from the right.
As October puts four states with large Hispanic populations - Florida, Colorado, Nevada, and New Mexico - at the center of the presidential contest, what appeared at first to be a possible strength for McCain has emerged as a profound weakness.
"I feel bad for McCain," said Sam Rodriguez, the president of the National Hispanic Christian Leadership Conference and a prominent supporter of George W. Bush in 2004, who is neutral this year. "We find ourselves between the proverbial rock and the hard place. We really like John McCain. We really don't like the Republican Party."
Democrats relish McCain's quandary.
"It's hurt him in every way," said Simon Rosenberg, the president of the New Democrat Network, which has focused on bringing Hispanics back to the Democratic Party. "I don't think it's assured the right he's really with them. And for those who are immigration reform advocates, he's become a betrayer, having been a leader."
Since America's economic crisis deepened this fall, immigration has almost entirely vanished from the national conversation. Three debates have passed without a single mention of the issue. And the undertow has pushed Hispanic and anti-immigrant voters alike toward the Democratic Party.
But under the radar, McCain and Obama are slugging it out in a bitter exchange of attack ads on Spanish-language radio and television.
Obama's goal has been simple: To associate McCain with the anti-illegal immigrant Republican right. One ad - which even some of Obama's allies declined to defend - associated McCain with tough immigration-related rhetoric from Rush Limbaugh. McCain countered with an ad accusing Obama of distortions and, less credibly, of having killed last year's immigration reform measure himself.
Obama, whose Spanish-language barrage also touches a range of economic issues, responded with a more defensible attack ad, saying McCain "surrendered to the anti-immigrant movement" by saying he wouldn't vote for his own immigration reform bill.
"We're seeing the most aggressive Spanish language communication campaign for president that the state of Florida and the country has ever seen," said Fernand Amandi, the executive vice president of Bendixen and Associates, a polling firm that advises Obama.
Amandi said that some had also falsely assumed that because McCain shared Bush's moderate position on immigration, he would inherit Bush's support.
"President Bush making his life and career in Texas grew up with Hispanics, always had Hispanics in his inner circle and in his kitchen cabinet, and had a genuine respect for the culture," he said. "There was never an emotional connection, there was never a personal connection, between McCain and the Hispanic community."
McCain advisor Ana Navarro called the attack ads "pathetic ploys," and conceded that McCain is being dramatically outspent on the Spanish-language airwaves.
"Obama is trying to do with $20 million what John McCain has done with over 20 years of service," she said, citing a figure relased by the Obama campaign. "We don't have that kind of money to spend."
Nonetheless, McCain continues to push hard for the Hispanic vote. He spoke about his plan to buy up bad mortgages in an interview with Univision Thursday, and he has offered almost nothing to the anti-immigration wing of his party since sewing up the Republican nomination.
Recent Gallup surveys show McCain with just 26 percent of the Hispanic vote.
Meanwhile, McCain is getting little affection from the other end of the spectrum either: anti-immigration conservatives.
"There's no substantial difference between the candidates on the underlying issue," said Steve Camarota, the research director of the Center for Immigration Studies, which advocates for restricting immigration.
To some analysts, McCain is ignoring a major chink in Obama's armor, though one which may have less salience now that the economic crisis dominates the headlines. When Obama said last fall that he would support states' decisions to issue drivers licenses to illegal immigrants, Hillary Clinton's pollster Mark Penn told her staff that Obama might have just lost himself the election.
"We thought he was going to get killed over it," recalled a Clinton staffer, who said Penn's polling portrayed it as so "lethal" that it could cost Obama the reliably Democratic state of California.
Views differ on why McCain hasn't exploited this issue.
"He just doesn't have the stomach for pandering," said Navarro.
Others say immigration never cut as deeply as pundits imagined, and point to the dismal failure of Colorado Rep. Tom Tancredo's single-issue presidential campaign.
"This issue has been a total loser, even inside the Republican Party," said Rosenberg.
And the shift of the campaign to the West and Florida may have simply made it too risky to antagonize his remaining Hispanic supporters, though some Democrats still think the issue may surface.
"Would McCain say, 'Screw it, I'm not picking up votes in these states, and would that be a Hail Mary? I wouldn't be surprised," said Frank Sharry, the executive director of the Democratic-leaning immigration group, America's Voice.
But as with other elements of his campaign, McCain may be battling forces beyond his control, as his advisor, Ana Navarro, noted.
"I don't think it has anything to do with John McCain," she said of his poll numbers.
Sam Rodriguez, the Hispanic evangelical leader who backed Bush, concurred.
"We really looked at McCain," he said. "If Bill Clinton was the first black president, John McCain could have been the first Latino president. Things were marching on until immigration reform failed."