His understanding of the stakes is apparent in the fact that he is investing $1 million in the Ames event — about one-fourth of the $4.2 million he raised in the second quarter.

Pawlenty emphasizes, as tortoises will, the long run. His campaign believes that Bachmann is potentially a flash in the pan whose campaign is brittle because of her propensity to say peculiar things (e.g., about Concord, N.H., the Founders and slavery, John Wayne). Pawlenty’s problem is the short run — between now and Saturday.

If Paul finishes first or second, the political community will shrug: There he goes again, the Babe Ruth of straw polls. If Paul and Bachmann, in either order, capture the two top spots, Pawlenty’s campaign may be mortally wounded. If another candidate propelled by an intense faction — former Pennsylvania senator Rick Santorum, a favorite of evangelicals who in 2008 were 60 percent of Republican caucus participants — also finishes ahead of Pawlenty, the Ames circus will have destroyed the only one among the six candidates who bought space — and therefore are permitted to speak — at the event who has a realistic chance to be nominated and defeat Barack Obama.