DES MOINES, Iowa - A squeaker of an Iowa victory behind him, a smiling Mitt Romney jetted to New Hampshire insisting that his staying power sets him apart from caucus runners-up Rick Santorum and Ron Paul and the rest of the GOP presidential field. Michele Bachmann underscored his point by quitting the race, and Rick Perry wavered.
      The withdrawal of Bachmann, who called herself the true conservative of the bunch, left her supporters up for grabs as the pace of the campaign quickens. That could boost Santorum, whose appeal to Christian conservatives in recent weeks lifted him from the dregs of the opinion polls to become Romney's top challenger and the conservative of the moment. "Game on," Santorum declared.
      Romney was named winner in the wee hours Wednesday - besting Santorum by just eight votes - bringing down the curtain on an improbable first act in the campaign to pick a candidate to challenge President Barack Obama in the fall.
      Romney, the former Massachusetts governor, and Santorum, the former Pennsylvania senator, each collected almost a fourth of the vote. The Iowa GOP said Romney got 30,015 votes, to 30,007 for Santorum.
      Romney shrugged off the promise of sharper criticism from his GOP rivals and Obama's re-election team now that he's narrowly affirmed his front-runner status.
      "I've got a big target on me now," he said Wednesday, adding that it doesn't faze him. "I've got broad shoulders. I'm willing to handle it."
      Fourth-place finisher Newt Gingrich got the attacks off to a quick start, saying the Iowa caucus results show "three out of four Republicans repudiated Mitt Romney. How can you take seriously somebody after that kind of campaign?"
Santorum, Gingrich, Perry and Bachmann argued persistently that Romney wasn't nearly conservative enough on the economy and social issues such as abortion and had vied for months to emerge as the alternative.
      Romney is heavily favored in New Hampshire's Jan. 10 primary, with contests in South Carolina and Florida packed into the final weeks of the month.
      Bachmann, the Minnesota congresswoman who finished a distant sixth, announced in Iowa that "I have decided to stand aside."
      Bachmann, who was born in Iowa, had won the state's GOP straw poll last summer before plummeting in the polls. Her loss there was devastating. Bachmann said she had run to counter what she called Obama's "socialist policies" and would continue her fight to overturn his health care plan.
      Perry, the governor of Texas, told supporters after his fifth-place finish that he was reconsidering his campaign. But Wednesday he announced via Twitter that he was still in the running: "And the next leg of the marathon is the Palmetto State. ... Here we come South Carolina!!!."
      Meanwhile, Romney was set to add to his already formidable national network Wednesday with the endorsement of Sen. John McCain, said a Republican official who spoke on condition of anonymity to avoid pre-empting the announcement. McCain twice won the New Hampshire primary and was the GOP presidential nominee in 2008.
      In a sign of the acrimony ahead, Santorum said McCain's nod was to be expected and took a jab: "John is a more moderate member of the Republican team, and I think he fits in with Mitt's view of the world."
      Despite its importance as the lead-off state, Iowa has a decidedly uneven record of predicting national winners. It sent Obama on his way in 2008, but McCain finished a distant fourth here.