Mitt staying in -- to keep McCain from clinching?

Ambinder and Geraghty hear that he’s pressing ahead and that tomorrow’s CPAC speech will be somehow “major.” Really? Major enough to make up a 500-delegate deficit? He can’t win — but neither can McCain, maybe. From the California thread, an e-mail from reader James P.:

All Mitt (and Huckabee) need to do to deny McCain enough delegates to win the nomination is win 547 of the remaining 963 delegates – roughly 57%. Which means it will go to the convention, where anything can happen. Given that around 66% of Republicans voted for someone other than McCain last night, it’s not out of the question, especially given most of the upcoming contests are awarded on a proportional basis and McCain won’t be taking primaries outright (like he did last night).

A prevent defense? Geraghty’s thinking about it too and speculates that the plan may be to make it to the convention and then squeeze McCain for concessions. But concessions about what? There’s no way Maverick’s putting him on the ticket and there’s no issue so central to Romney’s candidacy that he’d be willing to run on it for another 2-3 months with no hope of winning and who knows how many more millions down the sinkhole. Or is there? A scorched earth campaign to pull McCain to the right on immigration would buy him goodwill with the base for 2012 but it’d also alienate the party establishment he’ll need to woo next time by dragging out the nomination process. Plus, he’d have to do it in a way that made it look like he was running on principle instead of acting out of spite. Tancredo could pull that off since his passion for his signature issue is famous, but what’s Romney’s passion? Tussling with McCain? If he’s going to frame it as a “stop the RINO!” crusade, which perhaps is what he has in mind for CPAC, then he runs into the recurring problem of Huckabee running that same campaign against him, and pretty successfully too. And even if it worked and he forced a brokered convention, Maverick will be so close to having enough delegates to clinch that he’ll end up as the nominee anyway. The only question is whether Romney will have bought himself anything by dragging him around the country through the spring.

What’s to be gained by Mitt dropping out, you say? A lot, potentially. Right now Huckabee has leverage over McCain. Maverick may need his delegates at the convention, and even if he thinks he won’t, he needs the race to end as soon as possible, before he suffers any more credibility-destroying red-state losses. The longer it drags on, the more delegates Huck wins, the more likely he is as the VP choice. The way to destroy Huck’s leverage is for McCain to stay out there on the trail and pile up the 44% or so of remaining delegates that he needs to clinch, but as James’s e-mail notes, that’ll be tough to do in a three-man race. In a two-man race, with Mitt out of the picture, it’s easy — so much so that Huck may throw in the towel for fear of pissing off McCain and that same party establishment he’ll need for his own 2012 run. Once he’s out it’s a walkover for Maverick, he can pick the veep of his choice, and Huckabee gets a prominent role at the convention plus the gratitude of Republican bigshots various and sundry for being a good soldier. Exit question: Reason enough to hope Mitt drops out?