I’ve been doing a series of Veepstakes advice posts. So far, I’ve recommended that presidential nominees stick, if possible, to candidates who have been vetted by the process of running a national campaign, and that they avoid selecting anyone with minimal experience in office. Here’s another one: Don’t worry about the “chemistry” between the two candidates.

Warning: What follows is not exactly a perfect analogy, but I’m going with it anyway.

The danger is that candidates will make a Mark Portugal problem. Who? Baseball fans will recall that Mark Portugal was a journeyman starting pitcher of the 1980s and 1990s. Die-hard San Francisco Giants fans, myself included, may recall more: that Portugal was at his best against the Giants and that the team subsequently went out and made him one of the more ill-advised free-agent acquisitions of that era. Thus, a Mark Portugal problem is when you ignore all the evidence that’s out there except for what you see with your own eyes. It’s easy to make; we’re not good at placing the evidence we know the best into an overall context. That’s why, for example, everyone ignored the Alaska and Hawaii delegate-selection events; the results happened outside of prime-time viewing in the Eastern time zone, where most political pundits live. They have less of an effect on us if we read about them later instead of watching Wolf Blitzer total up the numbers and call the state with big dramatic music.

So: Mitt Romney’s been out campaigning with Paul Ryan across Wisconsin recently, and talk has started about Ryan as a Veepstakes player. And some of that talk is about the “chemistry” between the two on the campaign trail. To which I’d say: Who cares whether they have chemistry on the campaign trail? The ticket rarely campaigns together anyway; after all, you want to hit twice as many local markets. When the two people on the ticket do campaign together, it’s not very clear whether how much they appear to enjoy each other’s company matters very much, anyway. After all, most of the time the soundbite the campaign will want the networks to take (which is, at best, what you can hope that any real undecided voters will see) is usually going to feature just the presidential nominee delivering the day’s key talking point.

Sure, good chemistry will buy you a few minutes of nice coverage over the course of the campaign that a solid Reagan/Bush, Bush/Cheney or Obama/Biden ticket didn’t get (solid in the sense that the VP pick was electorally safe but not thrilling). That’s worth …well, it’s not worth very much. And besides, a good communications team can spin up almost any relationship as if it’s chock full of chemistry.

Bottom line: Do no harm remains the best course when it comes to the vice presidential pick. Beyond that, perhaps you can hope for a couple of percentage points of help if the running mate is popular in his or her home state. But chemistry just isn’t going to matter in November.