I've made a little hay here and in other places on the Internet about John McCain's lack of trustworthiness when it comes to selecting judges and justices for the Federal bench. All of this, of course, was within the context of a competitive primary election.
Although I still don't totally trust him, turns out that in 1998, John McCain was one of 29 Republican Senators who voted against confirming the nomination of Sonia Sotomayor to the U.S. Second Circuit Court of Appeals. Given that Sotomayor, whom Jeffrey Rosen at Slate recommends as a Supreme Court nominee should the Dem nominee for President win the general election, is both female and Hispanic, McCain took a fairly significant political risk in voting against this otherwise presumptively leftist judicial activist. (h/t Ed Whelan)