It's not so crazy. Perhaps McCain could become the Lieberman of the GOP by blasting Bush's commutation of Libby's sentence.
McCain's campaign is ailing, with less money on hand now than Ron Paul. If I'm counting correctly, he's the only serious candidate for the GOP nomination for President who hasn't commented on the Libby affair. If he's in dire straits, this could be the issue that reestablishes his maverick status and gets him some new support, making him the Lieberman of the Right.
The right-wing base would retch, but they're already leaving him anyway. The moderates and undecideds who once saw him as a maverick would see him so again, it would distract from his immigration bill woes, and it would give him a unique way to differentiate himself from the crowd.
I guess this makes me a borderline concern troll for the McCampaign, but dammit someone on the their side of the aisle has to show some cojones and stand up for what's right. Now's the time.