"If you don't agree with the "Gang of 14" solution then I am not your candidate and you should vote for someone else." -- John McCain

From The Conservative Case Against John McCain In 2008,

Just as Republicans in Congress were about to step in and put an end to the Democratic filibusters of judges once and for all, John McCain and the rest of the "Gang-Of-14" stepped in with a deal that kept the filibuster alive. This got John McCain and the other participants in the deal lots of favorable press, but the GOP paid a real price so that the "Maverick" could be in the spotlight again. Several GOP judges were thrown over the side and have, as of yet, never been allowed to get a vote.

Furthermore, the Gang-of-14 deal explicitly no long applies after the 2006 elections occur. So, if the Democrats gain seats in the Senate and decide to start filibustering again, it's entirely possible that this time, the GOP won't be able to muster the votes to stop them. That means that if a liberal Supreme Court Justice steps down during the last two years of Bush's term, because of John McCain and Company, it may not be possible to replace them with another Alito or Roberts. That's the price the party may have to pay so that John McCain can continue to be the New York Times' favorite Republican.