Mitt Romney is rolling out his running mate in the morning, and all signs appear to point to Wisconsin Member of the House Paul Ryan. It’s a high-risk, low-reward pick. Mostly recapping what I’ve been saying about Veepstakes for the last few months:

Political scientists generally have found that good running mates do little to help the ticket in November beyond the possibility of adding a couple percentage points in the vice-presidential candidate’s home state. That is, Paul Ryan is a low-reward pick because all running mates are low-reward picks. Perhaps it’s a little lower than usual: as someone who only represents one congressional district, Ryan is presumably less well known and liked in his home state than typical picks who have won statewide, although since picks from the House are rare, it’s hard to really know.

However, a poor pick can hurt the ticket some nationwide, although probably the only two to really do that over the years were Sarah Palin in 2008 and Tom Eagleton in 1972. Other picks that performed poorly during the campaign – Richard Nixon in 1952, Dan Quayle in 1992, perhaps Geraldine Ferraro in 1984 – haven’t been shown, as far as I know, to have cost any significant number of votes.

Paul Ryan is high-risk for one basic reason: most of the picks who have done badly during the campaign or in office or have looked bad after the fact have one thing in common: very little high-level campaign experience. Those who have survived a presidential campaign or at least multiple statewide (governor or Senate) campaigns have a much better track record. Yes, Ryan has been on national TV quite a bit, but doing that even as a very high-profile Member of the House is just not even remotely in the same ballpark as a national campaign, or even a statewide campaign. That doesn’t mean that he’ll do badly; there’s no obvious alarms as there were with Sarah Palin, who was (incredibly) chosen despite an active ethics investigation against her.

That’s not to say that Ryan will in fact wind up as a pick who hurts Romney in November. It’s just that it is not safe to assume that the clear political skills he’s shown inside the House will translate well. He has, for example, considerably less high-profile debate experience than even the Sage of Wasilla had last time. He’s totally unknown as a national candidate, and it’s hard to predict whether he’ll come across as “presidential” over the next few weeks. We don’t know how he’ll deal with this kind of attention, and while there have been several national profiles of him, we can expect some sorts of embarrassment to be dug up, and we have no idea how he’ll deal with that, either. Again, there’s just a lot more risk here than I think most people realize.

Now, beyond that, three points. First, I would downplay to some extent the idea that picking Ryan will establish the “narrative” of the rest of the campaign in any particular way. For the last few months, the veepstakes have been the biggest game in town; if Ryan does reasonably well, he’ll tend to disappear after the convention. That’s what running mates do. Barack Obama was going to hit Mitt Romney hard on Medicare and the rest of the Ryan budget (which is, in fact, a radical document which puts the Republicans behind any number of highly unpopular positions), but it’s a mistake to believe that having Ryan on the ticket will necessarily make that worse. Again: picking Ryan does not mean that the rest of the campaign will be “about” Ryan’s ideas unless either Team Obama wanted that anyway or this signals that Team Romney wants it now.

Second, Ryan will almost certainly be seen over the next week or three to have “energized” the party. That, too, is almost certainly overstated. Most of that “energizing” effect is structural, and would have happened regardless as long as Romney chose a “solid conservative”.

Third, I don’t think it will doom the campaign or anything like that, but it is worth noting that this is a shockingly inexperienced ticket, especially when it comes to national security and foreign policy. Dan Drezner wrote about Ryan and foreign policy back in the spring, and it’s worth looking at, but there really isn’t much there, I don’t think. Governors almost always pick someone with serious foreign policy or national security credentials, and one would think that would be particularly true with the nation still at war. The only ticket I can think of that was similarly lacking in foreign policy credentials would be Carter-Mondale in 1976, but at least both of them had military service in their backgrounds.

The bottom line about virtually all vice-presidential picks is that they seem far more important to the campaign when they’re made than they turn out to be. That’s probably true for this one, too. But if it does end up having a significant effect in November, it’s almost certainly going to be on the downside, and that’s more likely with Ryan than it would have been with most of the other reported finalists.