Republican presidential candidate Mitt Romney introduces himself to voters at the Iowa State Fair last week in Des Moines. (Chip Somodevilla/Getty Images)

And perhaps the one person for whom the game has changed the most is front-runner Mitt Romney.

The developments surrounding this weekend’s Ames Straw Poll had several of the keenest observers in politics suggesting there is now both an opportunity for Romney to win the Iowa caucuses and a new onus on him to, at the very least, compete there.

“He’s got to come and campaign aggressively,” Iowa Gov. Terry Branstad (R) said Sunday on NBC’s “Meet the Press.” “If he gets blown out in Iowa, I think he’s in real trouble.”

The Romney-must-now-compete-in-Iowa theory goes like this: Rep. Michele Bachmann is still not broadly seen as a real threat to steal the Republican nomination from Romney. While she remains the favorite in Iowa, few believe she can carry that momentum through a drawn-out GOP nomination battle with the likes of Romney, who is favored to win New Hampshire and Nevada and could also win the South Carolina primary.

Perry, on the other hand, is seen as more of a long-term threat, and a win in Iowa by Perry would be much more dangerous to Romney than a Bachmann Iowas victory.

While Romney is a heavy favorite to win in New Hampshire and Nevada, Perry may be favored to win in South Carolina. That means, if Perry wins Iowa, he could notch two of the four early states and really give Romney a run for his money in the nomination war.

All of that suggests Romney needs to play in Iowa. But there’s also evidence that he’s got better odds in that state now too.

That’s because Perry entrance into the race now splits the anti-establishment vote with Bachmann, while Pawlenty supporters are more likely to be in Romney’s corner. That puts Romney in better position to win Iowa with a lower percentage of the vote than he would have needed in more of a head-to-head contest with Bachmann.

And all of that goes double if Sarah Palin gets in the race.

GOP strategist Mike Murphy told The Fix that, “in a race with Perry, Bachmann, (and former senator Rick) Santorum, there is still a lot of regular GOP vote Mitt could go after.”

Murphy pointed out that, in 2008, the more establishment-friendly GOP candidates took 55 percent of the vote in the Iowa caucuses – a number that suggests there are lots of votes for Romney to collect with Pawlenty out of the race.

Those voters, of course, could also side with Perry. While Bachmann’s support is heavily concentrated in the tea party wing of the GOP, Perry can cull votes from the tea party and establishment wings. But that also gives Romney incentive to focus real effort in the state, because any votes he can win would likely come at Perry’s expense and, at the very least, hurt Perry’s chances of winning the state and gaining momentum.

Romney’s team declined to comment on its strategy in the state. Romney himself has only been there twice this year and did not play in the straw poll, but he has assured he will compete in the caucuses. The question is, to what extent?

For their part, Perry’s supporters are practically daring Romney to seriously contest the state.

GOP strategist Henry Barbour, who supports Perry, told The Fix that Romney was being “timid” by dancing around whether he would seriously contest the state.

“I don’t understand why Gov. Romney would not want to compete in Iowa; he looks good in the polls there,” Barbour said. “If Teddy Roosevelt was a campaign consultant to Mitt Romney, do you think they’d be so timid? As TR said, you don’t want to ‘be with those cold and timid souls who neither know victory nor defeat.’”

Perry was blunter: “If you’re not in Iowa, you ain’t happening.”

Whether timidity or something else, this careful and measured approach has been an early hallmark of Romney’s campaign. And so far, it’s worked for him.

But we’re getting to the point where we could be as few as four months away from the Iowa caucuses, and Saturday’s Ames Straw Poll set the stage for the race ahead between the top tier contenders: Bachmann, Perry and Romney.

Romney’s brand right now is one of a guy who was really seen as the only candidate with the momentum and organization to win the Republican nomination.

Perry is still largely undefined as a presidential candidate and untested on the national stage. And in fact, he could flame out just as easily as he rose. But more than Bachmann, he threatens Romney’s status as the consensus frontrunner, and Romney’s team has to figure out how to deal with the newcomer.

If the Romney campaign doesn’t put its best foot forward in Iowa, it would definitely be giving Perry an opening. But running hard in the Hawkeye State also risks the embarrassment of a loss for Team Romney, as we found out in 2008.

This is perhaps the biggest strategic question of the campaign post-Ames.

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