Only one side can be right about Paul Ryan, so which is it?

This guy? Really? But why? Republicans appear to be extremely enthusiastic about Mitt Romney's selection of Paul Ryan as his vice-presidential nominee, but Democrats are also elated, because Ryan's now-infamous Medicare-ending budget makes for such a fat, juicy target. I've been wracking my brain all weekend as to why Romney made this choice, wondering if there's something I've missed, something we could be wrong about as to why we're in the right about the political merits of this decision. I'm still coming up empty. Here are the alternatives I've considered:

• Republicans don't think the Ryan plan is a liability. This flies in the face of tons of polling data, the fact that Democrats have spent millions on ads attacking various GOP candidates for their support of the Ryan plan, and even the reality that Democrats won a special election upset last year in a very red upstate New York district thanks in large part to the role the Ryan plan played in that race. But it's still possible for Republicans to imagine that they just haven't had the chance to explain Ryan's budget properly, a delusion probably abetted by the conservative belief that the libruhl media has conspired against them. With Ryan on the ticket, the media will have to give the plan a fair shake (so the thinking goes), and Ryan will also be able to sell it before a national audience in a way no other politician can. Crazy, but I could see them believing it. After all, they already believe all kinds of insane shit.
• Republicans think that the Ryan plan, and Paul Ryan himself, will motivate their base more effectively than Ryan can be used as a bludgeon by Democrats. This makes more sense if you believe that 2012 will be a "base election," and it fits in line with Romney's strange refusal to tack to the center after winning the nomination. It's still probably wrong, though. For one, hatred of Obama matters far more to movement conservatives than any qualms about Romney's ideological purity'these people are going to come out and vote against the Kenyan Muslim socialist usurper no matter what. For another, as I discussed just above, the Ryan budget, particularly the "end Medicare" aspects, are very powerful motivators for Democrats. Indeed, the Ryan plan is so extreme that polling has shown some Democratic attacks based on it have fallen flat because voters refuse to believe anyone would ever propose such a thing. That problem just got erased.
• Republicans know Ryan is a liability, but they see the electoral math looking very tough for Romney and feel they need another Palin-esque Hail Mary. Again, this makes some sense if you subscribe to the "base election" theory and believe Romney needs a real firebrand to motivate the movement conservatives. But then why would you pick Ryan? There are other options, aren't there? Marco Rubio, Chris Christie, Pat Toomey, Rand Paul if you really wanna get out there. So why not go with someone whose very name isn't on the cover of the plan that would end Medicare as we know it? Well, it's possible that each of the other plausible alternatives failed the vetting process somehow. It's also possible that ...
• The Republican vetting process is still fucked, and Ryan's negatives simply weren't properly taken into account or weren't properly understood. The GOP has had a very strange run of vice presidential candidates lo these past many years. Obviously Palin stands out (and always will), but do you remember how dark lord Dick Cheney was picked? Why, he was head of the selection committee ... and then chose ... himself! Before that, in 1996, Republicans went with Jack Kemp, a quirky outsider who was loathed by presidential nominee Bob Dole. And before that, well, there was Dan Quayle. So it's been a long time since the Republican VP selection process has really made sense'I think you have to go back to 1980, when Reagan tapped Bush Sr. So I could see Ryan passing muster with a lazy or incompetent selection committee.

Maybe I'm wrong about all this. Maybe the GOP's crack squad of interrogators polled and focus-grouped this one to death, finding that Ryan is a bonus to them and no help to us, perhaps in concert with the expectation that Romney will be able to out-spend Obama in the stretch run. I'm nervous about that possibility, but I'm still skeptical of it'I still think they're wrong and that Romney has made a real mistake here. But as to the four alternate theories I've proposed, I can't decided which I think is more likely to be right. What do you say? Alternate explanations are heartily welcomed.

10:39 AM PT: Well, here's one bit of insight into the Republican mind. NRCC political director Mike Shields send a presentation to various GOP candidates (which you can view at the link) explaining how they think the Ryan plan needs to be dealt with:

"The media is eager to write stories that we are suddenly on defense and that choosing Ryan for VP will cost us votes with seniors. This is absurd since a. the Democrats were going to hit us on the Ryan plan anyway and b. we have proven you can successfully push back so long as you play offense," Shields writes in his message.