Former Massachusetts governor Mitt Romney is something close to a perfect Republican candidate: handsome, charismatic, an encyclopedic knowledge on a ranges of issues, quick on his feet and so on and so forth.

But, Romney has exhibited one major flaw throughout both his 2008 and 2012 presidential bids: He doesn’t like to be aggressively challenged — either by his rivals or by voters/hecklers — and when he is, he often makes mistakes or looks something short of presidential.

Former Massachusetts Gov. Mitt Romney, right, answers a question and former Pennsylvania Sen. Rick Santorum listens during a Republican presidential candidate debate at the Capitol Center for the Arts in Concord, N.H., Sunday, Jan. 8, 2012. (AP Photo/Charles Krupa)

* $10,000 bet : When challenged by Texas Gov. Rick Perry about removing a chapter about the individual mandate from his book, Romney responded by challenging Perry to a $10,000 bet. Of course, normal people don’t bet $10,000 and it made Romney looks badly out of touch and reinforced the “rich guy” narrative that doesn’t help him in the campaign. It was, without question, his worst moment in any debate.

* “Corporations are people, too”: Speaking at the Iowa State Fair just days before trhe Ames Straw Poll, Romney was being heckled about his defense of big business by some Democratic activists. “Corporations are people too,” he said — a line immediately picked up by Democrats as evidence that Romney was (you guessed it) out of touch.

* The shoulder touch: Perry went on the attack against Romney on illegal immigration in a mid-October debate, alleging that the former Massachusetts governor’s use of illegals as lawn care workers gave him no credibility on the issue. A visibly irritated Romney reached between the podiums and touched Perry’s shoulder — a major no-no in debates where personal space is sacred.

* “It’s still my time”: When challenged about whether or not he would limit himself to one term by former Pennsylvania senator Rick Santorum during Sunday’s “Meet the Press” debate, Romney responded “it’s still my time” when Santorum attempted to interrupt. This is one of a number of exchanges during the debate in which Romney when challenged tries to either a) appeal to the moderators for intercession b) appeal to the rules of the debate in an attempt to short-circuit an attack. (More on that below.)

* Bret Baier interview: Romney was decidedly testy when asked by Fox News Channel’s Bret Baier whether and why voters should believe that the positions he currently takes are ones he will stick by if he becomes president. “Your list is just not we are going to have to be better informed about my views on issues,” Romney scolded in an interview that was surprisingly confrontational and drew negative headlines to Romney.

The Romney team, not surprisingly, rejects the idea that he doesn’t do well with confrontations — insisting that most of the episodes detailed above cast him not as short-tempered but rather as a leader not willing to put up with any bull either from his rivals for the nomination or from hecklers. Romney, as the frontrunner for the entirety of the race, also takes far more slings and arrows than his opponents for the nomination and so by pure volume alone has a higher chance of reacting poorly to them.

And, it’s also worth noting that almost everyone — the Fix included — tends to avoid confrontation and when it comes doesn’t react as we might like to with hindsight being 20-20.

Of course, not everyone is running for president. Mitt Romney is. And, to hear one former adviser to Romney tell it, his struggles with confrontation are part of a broader Achilles heel for him.

“It goes back to his inability to talk with people,” said the source. “He can talk issues like the economy but he’s not a guy you sit and have a beer with. Getting challenged is kind of the same thing.”

The source noted that the politicians who do the best when challenged — former Mississippi governor Haley Barbour, New Jersey Gov. Chris Christie — are “the personable guys, the back slappers...They can talk their way out of anything, including a confrontation and that’s just not [Romney’s] personality.”

(For evidence of Christie’s ease when dealing with adversarial questions, check out this You Tube clip that launched his national profile.)

We’ve long believed — based on direct observation of Romney and conversations with those who know him well — that the former governor’s success in a campaign setting is directly proportional to the number of rules that govern it.

So, in debates and big speeches — both of which are very rule-heavy, Romney excels because he can master the rules of engagement and then execute against them.

On the other end of the spectrum is stumping on the campaign trail. There is no blueprint for how to interact with voters in a diner in New Hampshire — remember the fake butt pinch? — or at a speech at the Iowa State Fair.

Ditto for confrontations — whether in a debate or on the stump. What Romney almost invariably reverts back to in these moments is an attempt to re-assert the rules (such as they are).

Go back and watch the Romney-Perry scuffle over immigration; “You get 30 seconds...this is the way the rules work here,” said Romney before appealing to CNN debate moderator Anderson Cooper for intercession.

To be clear, Romney’s struggle with confrontations hasn’t hurt him much — if at all — in the primary race to date. He is heavily favored to win the New Hampshire primary on Tuesday and, if polling is to be believed, is the frontrunner for the South Carolina primary on Jan. 21.

But you can be sure the Obama team has taken note of these Mitt-frontations and will do everything they can to poke at Romney if and when he becomes the Republican nominee. (The Democratic National Committee has already put out a web video highlighting the best “Mitt fits” of 2011.)

Confrontation is a part of politics — and life. Romney must get better at dealing with it before the general election begins in earnest.