Here is a fact causing Republicans to wonder why Mitt Romney isn’t the runaway favorite in his campaign to unseat President Obama: No U.S. president since Franklin Roosevelt has won reelection when the unemployment rate was more than 7.4 percent.

So why isn’t Romney the clear favorite? Because Obama remains more popular personally than one would otherwise expect. Because the Obama campaign has been more effective at sowing doubt about Romney’s record as a wealthy capitalist than the Romney campaign anticipated, which is evidence to some that Romney’s campaign isn’t overstaffed with brilliant strategists. And because Romney himself has the unfortunate tendency to come off as both artificial and superficial.

Even Romney’s allies know he lacks the chemical building blocks of likability. The Republican speaker of the House, John Boehner, was asked recently by a voter in West Virginia the following lamenting question: “Can you make me love Mitt Romney?” Boehner answered, in a plain-spoken manner, “The American people probably aren’t going to fall in love with Mitt Romney.”

Many of Romney’s problems arise from his lack of authenticity. This suggests that he should choose a running mate who conveys a feeling of he-just-can’t-help-himself genuineness. Which is why all the talk about Romney’s unwillingness to consider New Jersey Gov. Chris Christie for the vice- presidential slot is a bit of a mystery to me.

There are, to be fair, many reasons Romney might want to keep Christie off the ticket. Christie has an excessively large mouth. He is easily provoked. He turns up late to speeches on occasion. He doesn’t quit when he’s ahead. He is no one’s idea of a deputy. He comes from a state the Republicans can’t win, no matter what Romney does. He is a Northeastern laissez-faire Republican mistrusted by social conservatives. And, of course, he is unwieldy and overweight and makes Romney look anorexic by comparison.

On the other hand, if Romney wanted to actually win the presidency, he might consider choosing Christie.

I’ve been looking at Romney’s vice-presidential possibilities for the past couple of weeks (yes, I know, I need to find a better hobby), and I’ve been struck by two things. The first, as The Washington Post columnist Michael Gerson has noted, is that the field of Republican vice-presidential hopefuls is much more impressive than was the field of Republican presidential hopefuls. (My apologies to fans of Michele Bachmann and Herman Cain.)

The second is that the most talked-about candidates, while in possession of impressive resumes, are almost comically bland. The first rule when picking a vice-presidential running mate is, of course, don’t pick Sarah Palin, or anyone who might remind the voting public of Sarah Palin. The people on Romney’s short list — which includes Ohio Sen. Rob Portman, former Minnesota Gov. Tim Pawlenty and Wisconsin Rep. Paul Ryan — do not resemble Palin in any way. Romney is safe with any of these candidates.

Will he fill arenas with them? Are any of these candidates particularly skilled at speaking to disaffected blue-collar workers, to Reagan Democrats, without condescension? Pawlenty has a blue-collar background, but he didn’t connect with the white working class, or with anyone else, in his abbreviated run for president.