Yglesias notes that objections to McCain and the “Gang of 14” are among the weakest raised by conservatives against the nominee, and this is right.  We have to remember that the “principle” at stake in this particular controversy was the ludicrous idea that filibustering judicial nominees was unconstitutional.  Since the filibuster is a creation of Senate rules, its use has nothing to do with the Constitution, which already gave the Senate power to make its own rules.  So, yes, it was a disagreement over tactics and maneuvering, but the larger problem was that the Republican leadership defended their preferred tactics of demagoguing the Democratic threat of a filibuster by taking an inherently absurd position.  McCain’s great error, such as it was, was to back away from the foolishness of the so-called “nuclear option.”  The creation of the “Gang” effectively avoided the need to make an end-run around the use of cloture.  As an episode of parliamentary maneuvering, McCain comes off looking much less ridiculous than Frist et al. 

But even this does not really explain why this looms so large in the minds of many of McCain’s mainstream critics.  The reason that it keeps being brought up is that the “Gang” episode embodies what it is that most Republican partisans dislike about McCain the most: his willingness to break with leadership or go against the majority of the party.  If this sort of behaviour is seen as intrinsically wrong in most cases, Republican partisans see it as especially awful when it comes to the confirmation of judges.  It doesn’t matter whether McCain’s move may have made more sense under the circumstances of a limited Republican majority–it was the fact that he turned against the leadership and was consorting with them on something as important as judges, even if, in the end, he actually voted to confirm all the judges that conservatives wanted to see confirmed.  Of course, the position the leadership took against filibustering of judicial nominees was also extremely short-sighted, since it now effectively puts the Republican minority at a significant disadvantage in resisting any future Democratic appointments. 

Ultimately, this has become an issue because of McCain’s unwillingness to be a team player.  Objectively, from a conservative perspective Romney was a far, far more compromised candidate when it came to his record, but he was a team player who seemed quite happy to adopt an entirely new set of policies to that end, while McCain is interested in his own advancement and cultivating the favourable media coverage to achieve that.  So he makes these grand gestures to demonstrate that he isn’t a reflexive partisan, and journalists write glowing accounts of his “maverick” style.  Arguaby it is the favourable media reaction to McCain’s rebellions that makes those rebellions seem even worse to Republicans who are already unhappy with them.