[Guest post by Walter Shapiro]

Tim Pawlenty’s formal presidential campaign lasted less than 100 days—a stunning, scandal-free collapse for a man who, until recently, was considered a top-tier GOP contender. But even though Pawlenty flamed out with a weak third-place showing amid the vote-buying, corn-dog hokum of Saturday’s Iowa Straw Poll, there was a sense of inevitability to his political demise.

From the beginning, Pawlenty probably was doomed to see his presidential dreams die in the corn fields of Iowa. As the former two-term governor of neighboring Minnesota, he could not credibly pull a John McCain and skip the caucuses. But Pawlenty lacked personal wealth, a major-league fund-raising network, and intense ideological appeal. So to keep the money flowing until the 2012 caucuses, he needed a breakthrough moment, the stuff that news-magazine covers used to be made of.

Pawlenty was caught in a fund-raising Catch-22—running out of money, he had to squander it all on the Straw Poll. Sure, there were discussions inside the Pawlenty campaign about skipping the Straw Poll after Mitt Romney announced that he was not competing. But, in the end, going AWOL was never a serious option for a candidate desperate to survive 2011. As a result, Pawlenty was condemned to compete in Saturday’s rigged game by trying to win the hearts and minds of 17,000 Iowa Republican activists who considered Michele Bachmann, Ron Paul, and Herman Cain to be Oval Office material.

Even though he tried to position himself as a right-wing firebrand, Pawlenty was never going to win a competition as the Republican who shouts the loudest about breaking Barack Obama’s knee caps. Pawlenty, at his core, is a nice-guy conservative who wants to cut taxes rather than storm the barricades. His gubernatorial record, his blue-collar South St. Paul roots, and his Midwestern affability might have been an appealing mixture in other political years and with other GOP constituencies. But not in 2011 and certainly not in the hot-house cauldron of Iowa Republican politics.

Pawlenty, to be sure, also made his share of rookie mistakes. His failure to go after Mitt Romney in the June New Hampshire debate, after signaling that he was going to challenge him over “Obamneycare,” helped produce a press-pack narrative of Pawlenty the Wimp. His Iowa TV ads often made it seem that he was already running against Obama rather than scrapping for Straw Poll votes with Bachmann. His plan-everything-out-in-advance political style—the hard-working striver’s ethos—turned him into almost as synthetic a candidate as Romney. Pawlenty, who got his start in Minnesota as a political operative, was running a traditional presidential campaign (formal policy speeches, far-flung campaign aides) in an unpredictable year.

Had Ron Paul won the Straw Poll (he finished only 152 votes behind Bachmann) or had Rick Perry entered the presidential scrum early enough to actively compete in Ames, Pawlenty might have been able to soldier on in Iowa. But short of rescuing a child from a burning building on national television, Pawlenty never would have been able to raise enough money to be a serious contender. Pawlenty’s decision to pull the plug the morning after the Straw Poll was both a realistic assessment of his chances and a dignified refusal to go through all the motions of a dying candidacy. It also allowed his staffers to get on with their lives—and it is telling that none of them are publicly bad-mouthing Pawlenty in defeat.

The Republican field right now is divided into two camps—pragmatists pretending to be wing-nuts and genuine ideologues. Pawlenty, even as he mouthed the far-right malarkey about the debt-ceiling vote, is a pragmatist with fewer policy reversals than Romney. He seemed like a plausible Republican nominee—in theory. The problem is that, in reality, Pawlenty had to survive that candidate-killer known as the Iowa Straw Poll.

Walter Shapiro is a special correspondent for The New Republic. Follow him on Twitter (lucky you).