Myopic Trump takedown could backfire: Ex-GOP gov

Tim Pawlenty: Trump's flaws 'already baked in the cake'

Attacking Donald Trump's character won't slow his march to the Republican nomination because his supporters accept his "warts," Mitt Romney's former campaign co-chair told CNBC on Friday.

Tim Pawlenty told "Squawk Box" he has "high regard for Romney," but the former governor of Minnesota challenged the premise of Romney's Trump takedown speech.

"The core of [Mitt Romney's] argument was Donald Trump has character flaws," said Pawlenty, who gave up his own presidential aspirations to support Romney in his failed bid for the White House in 2012.

"The people who are supporting Donald Trump have already factored in character flaws. I don't think they think Donald Trump is a saint. They know he's got a bunch of 'warts,' so to speak," said Pawlenty. "So it's already baked in the cake. And I don't think it's going to change much."

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Pawlenty said Republican leaders have promised grassroots conservative activists for years that they'll cut taxes, balance the budget, rein in spending, repeal and replace Obamacare, reform entitlements, and restore the military. "Eventually, you say, 'You're all full of B.S., and it's not working. We're going to try something dramatically different,'" Pawlenty said.

"[Trump supporters] are not voting on character. They're voting on change. It's not to say character is not important, but they want something very different. They want somebody to come into Washington and elsewhere, and sort of 'break the furniture.'"

Tim Pawlenty: I support Marco Rubio

The Republican Party would be best served if Florida Sen. Marco Rubio becomes the nominee, said Pawlenty. "I think you get all the upside with him without any of the downside: He's strong, but he's informed; he's conservative, but electable; he doesn't just talk about the American dream, he's actually lived it; and he's a person of good character. I think he's got the total positive package."

Pawlenty said there's still time to defeat Trump. "But you've got to consolidate the field down to one candidate. And they're not willing to do that." He acknowledged that Rubio, Texas Sen. Ted Cruz, and Ohio Gov. John Kasich were all unlikely to drop out anytime soon. "They can all make a rationale to stay in the race and they're all going to stay in the race. And that's going to defuse the non-Trump, the 65 percent of the vote, that isn't currently for Trump."

Still, Pawlenty stressed that he'd support whoever becomes the Republican nominee, even Trump. "It would be a very new adventure for all of us if Donald Trump is the nominee."

Pawlenty's worst-case scenario would be if one of the candidates were to enter the convention with a plurality of delegates but not enough to win the nomination outright. A brokered convention of backroom deals to consolidate delegates and decide the nominee would be disastrous heading into the general election, he said.

"My strong, strong advice and I'll say this as strongly as I can, hey look, compete; win it; lose it; but don't steal it; because if somebody gets in there and tries parliamentary monkeybusiness and steals away this endorsement, you'll have a massive mess on your hands," Pawlenty said.

"If you understand the modern day Republican Party, not at the donor level but at the grassroots level, these are people who are in it for their true beliefs and their cause," he said, adding they'll detest being told by party powerbrokers what to do. Such a scenario would be "disconnected from the modern-day grassroots movement."