Some pundits act confused by the fact the GOP no longer even pretends to have any policy goals, but it's always been possible to understand the actions of the GOP Senate Leadership as pure partisan gamesmanship. All of Mitch McConnell's actions during Obama's first term made perfect sense given his stated #1 priority: preventing a second term for the President.
That failed, but surely there is lots of stuff that McConnell still wants to obstruct, right?
So how do we make sense of his decision to push Dems over the edge on the filibuster? The Senate GOP has blown itself up. The Daily Koz asks: What the hell were they thinking?
The answer: expecting the actions of the GOP to make sense has become a fool's errand. The party is dying, and is likely to die in the manner popular in old war movies: staggering around, moaning incoherently.
Update: Another good piece that examines the irrationality of giving Harry Reid the votes to do this (by totally blockading all nominations to the DC Circuit) comes from Scott Lemieux in the American Prospect: Harry Reid's Triumph.