It was clear during Saturday night's debate at Drake University in Des Moines, Iowa, that Newt Gingrich's current frontrunner status makes him the prime target for his fellow Republican candidates.
Even some GOP lawmakers on Capitol Hill are voicing their concerns about him and have been reluctant to endorse the former House speaker.
"I saw the damage he did to the Republican party and to the Congress. And I think I owe it to my constituents and to the country not to allow that to happen again," noted Rep. Peter King, R-N.Y.
"If he did that as speaker, I'm really concerned about what he would do as our nominee for president," he added.
As a member of Congress in the late 1990s, then representative and now Sen. Lindsey Graham, R-S.C., organized a failed attempt to oust Gingrich as speaker of the House.
Graham said he believes Gingrich has matured since then but still won't give his endorsement.
"I think he's leveled out as a person and all of us, even his worst critics, would say that Newt is a guy that can really hold a room," Graham said.
Gingrich's Republican critics say he had a million ideas as speaker, but many of those were a distraction.
"You can say a lot of things about Newt, and he sometimes ruled with an iron fist. But you can't say he was a bad speaker. He was a change speaker who took the Republicans to the promised land after 40 years out of power," explained former Rep. Tom Davis, R-Va.
When asked about his Republican rivals, President Obama told CBS's "60 Minutes" Sunday night that Gingrich is a good debater and Mitt Romney is a good politician.
Gingrich starts this week with big leads in many of the early primary voting states.
He's scheduled to be in New Hampshire Monday for a Lincoln-Douglas-style debate with Jon Huntsman.