Obama campaign manager Jim Messina offered his year-out analysis of the 2012 race tonight in a lengthy email to supporters, underscoring the “Obama versus the GOP/Tea Party” narrative that he has been crafting over the past six months.

Messina uses a New York Times weekend analysis of the GOP field to shadow box the notion that some candidates may have a  better chance  against Obama than others.

“There has been virtually no difference among the GOP candidates — or between them and the Republican congressional leaders who refuse to do anything to restore economic security for the middle class,” Messina writes.

“Whoever wins the nomination will no doubt try to appear more ‘moderate’ as they compete for undecided voters in the general election. But they have all made their positions clear. And we will hold them accountable for that,” he said. “The only true difference in this race is between their agenda and President Obama’s.”

Messina says the Obama campaign’s army of supporters – more than 1 million enlisted so far – will make the difference in nine key battlegrounds Obama flipped four years ago.

“We have no intention of returning to the old electoral map,” Messina said, adding that he’s optimistic about Obama’s chances to gain ground in Arizona and Georgia, where Hispanic and African-American voters could play a swing role.

The Obama campaign has raised more than $88 million for the 2012 race and been rapidly expanding its grassroots organizing presence in states nationwide, including Arizona and Georgia.

Aides say the next two months, before the campaign kicks into a higher gear, will focus on energizing supporters and gathering commitments from volunteers to get involved.

“So, is Obama toast?” Messina asks in his email, “It’s up to you.”