Mitt Romney’s unopposed sweep of the five primaries yesterday brought him that much closer to the Republican presidential nomination that is already his in all but name. But it also will turn up the heat on the search for his running mate. With nothing else to discuss — other than the issues, that is — anyone whose name is under consideration can expect the sort of examination that has, up until now, been restricted to presidential contenders.

The chief recipient of this intense scrutiny will undoubtedly be the man many believe is the frontrunner for the number two spot on the GOP ticket: Marco Rubio. Along with the other main contenders, Paul Ryan, Rob Portman and Chris Christie, his career and life is going to get a going over with a fine tooth comb not just from Romney’s vetting team but from a press corps that no longer has a nomination battle to cover. One of the first shots at Rubio’s credentials came yesterday from John Dickerson at Slate, who attempted to tag the Florida senator as being another version of 2008 GOP veep pick Sarah Palin, which is about the most unflattering comparison possible.

According to Dickerson, Rubio is similar to Palin in that he hasn’t any executive experience. Therefore, because Romney is running on the issue of competence, Rubio’s presence on the ticket will undermine the Republican campaign. Of course, it should be pointed out that Palin actually had a lot more executive experience (both as mayor of Wasilla and her 19 months on the job as governor of Alaska when John McCain tapped her for the nomination) than Rubio. But the problem with this argument is the issue with Palin was not so much her relatively thin resume (though not when compared to Barack Obama) but her lack of comfort discussing the major issues of the day in depth and at length. Rubio is a relative newcomer, but he is not someone who will flame out and play the fool in a one-on-one interview with Katie Couric.

Rubio may not be the second coming of Dick Cheney — a man who was picked to run with George W. Bush because of his extensive Washington resume and ability to govern — but he is ready to debate on the national stage, something that, for all of her considerable political gifts, Sarah Palin was not prepared to do in 2008.

But Dickerson is on to something when he hones in on Romney’s obvious desire to have someone run with him who has executive experience or at least possesses the ability to approach the issues with the same systematic method Romney prized during his business career. If that is what Romney is looking for — and Cheney is right when he says the priority should not be on superficial political advantages that might attach to possible running mates — then the edge will go to the only sitting governor on the presumed short list: Chris Christie.

However, the other two main contenders also bring something to the table in this regard that should not be discounted. As the chairman of the House Budget Committee and the architect of the Republican proposals for entitlement reform, Ryan clearly has the vision and the understanding of how the federal government works to help Romney govern. And Portman, who currently sits in the Senate but was George W. Bush’s budget director, has the same sort of credential. But both also have negatives attached to their resumes. Ryan is considered radioactive to some because of the way Democrats have demonized his proposals, and Portman’s service in the last administration will link Romney to Bush.

Dickerson is also right to discount the edge that Rubio would bring with Hispanic voters. As I wrote yesterday, most of what is assumed by pundits about that is probably untrue.

As for Rubio, the jury is still out on whether his efforts to tamp down speculation about his candidacy were genuine. He had me convinced when he repeatedly said that “it wasn’t going to happen,” which sounded like he had a reason why he didn’t want to run (or why Romney shouldn’t pick him) rather than the usual coyness that we expect from vice presidential contenders. But his recent efforts aimed at self-promotion as well as a memorable Freudian slip about the subject have left me thinking maybe he wants it after all.

In the first century of the history of this republic, it was customary for presidential contenders to pretend they weren’t candidates and bad form to do anything that could be construed as campaigning for the job. But though that silly masquerade is no longer part of the presidential election process, it is retained for would-be vice presidents. But we’d all be better off if there was more candor about the veep search.