"I wish it would have been different, but obviously the pathway forward for me doesn't exist so we are going to end the campaign," Pawlenty said on ABC's "This Week" from Iowa.
The low-key Midwesterner, who had struggled to gain traction in a state he had said he must win, had told supporters on a conference call shortly before the broadcast interview that he was ending his White House bid.
"I thought I would have made a great president, but obviously that pathway isn't there," Pawlenty said. "I do believe we're going to have a very good candidate who is going to beat Barack Obama."
The two-term ex-governor of a Democratic-leaning state was on Arizona Sen. John McCain's short list for the vice presidential spot in 2008. He had spent roughly two years laying the groundwork for his 2012 campaign and had hoped to become the alternative to the national front-runner, former Massachusetts Gov. Mitt Romney.
But this summer he unexpectedly found himself in a grudge match with Minnesota Rep. Michele Bachmann, who shot to the top of polls in Iowa after getting into the race. Pawlenty struggled to raise money and connect with voters.
He poured most of his money and time into Iowa in the run up to Saturday's straw poll, a test of organizational strength and popularity in the state whose caucuses lead off the GOP nomination fight.
Pawlenty had acknowledged that he needed a strong finish in the straw poll to show momentum and quiet concerns that his campaign was faltering. He put it all on the line, spending the bulk of his campaign account on TV ads ahead of the contest and on a statewide tour of Iowa.
But Bachmann won and got two times as many votes as Pawlenty, who came in well behind the second-place finisher, Rep. Ron Paul of Texas.
Despite that, Pawlenty suggested to supporters late Saturday night that he wasn't dropping out. He called the test vote here "an important first step on the road to the Republican nomination and, ultimately, the White House.
"As I've said all along, we needed to show progress to do well, and we did just that," Pawlenty said. "This is a long process to restore America - we are just beginning, and I'm eager for the campaign."
Still, he said in a statement after the results were announced: "We have a lot more work to do."
Hours later, he reversed course in the face of a daunting challenge: convincing donors who were slow to give in the months leading up to the straw poll that he was still a viable candidate.
Had he stayed in the race, he would have been competing for money in an expanded field. Texas Gov. Rick Perry, a prolific fundraiser with deep ties to the party's biggest donors, became a candidate Saturday.
At first blush, Pawlenty, 50, seemed to have all the right ingredients as a candidate.
His blue-collar upbringing offered him a natural rapport with middle-class America. He governed as a fiscal hard-liner in a left-leaning state, winning his second term in a year when Republicans elsewhere got drubbed. He made inroads with the right crowds and assembled an all-star cast of advisers with loads of presidential campaign experience.
Pawlenty ran a traditional operation. In the lead-up to his campaign, he spread checks around to local politicians in key states through a political action committee while putting a heavy focus on small-scale events in places such as Iowa and New Hampshire.
But Pawlenty struggled to connect. He came off as bland and rehearsed next to more dynamic contenders. He languished in the polls. Perry's candidacy shoved Pawlenty further to the side.
His inability to stoke the passions of voters the way other candidates and even noncandidates have was evident.
"He said the right things, that we're going to limit the size of government and hold down spending," Sam Buck, a retired veteran from Winterset, said last week after hearing Pawlenty speak. "I like him ... but let's see what Perry of Texas does."
Pawlenty had been building momentum after a May campaign launch in which he framed himself as the one in the race willing to deliver the hard truths and confront public policy sacred cows. The climb screeched to a halt in a New Hampshire debate in early June, when he shirked the chance to back up prior tough talk about Romney when they were face to face. It reinforced worries among some Republicans that he wouldn't be willing to take the fight to Obama as the nominee.
In that same debate, Bachmann declared herself a candidate and immediately cast a long shadow Pawlenty had trouble escaping. When he went on the attack against Bachmann in an Iowa debate this week, some wondered if he came on too strong.
His ability to raise money paled compared with Romney and others. The straw poll showing threatened to discourage possible donors.
Associated Press writer Philip Elliott in Ames, Iowa, contributed to this report.