I was about to conclude that I could and should vote for John McCain (assuming he is the nominee) for the simple reason that at least one Supreme Court vacancy, and perhaps two or even more, will occur during the next President's first term.   The long-term prospects for conservatism are essentially hopeless if a Democrat President makes that/those nomination(s).   Or are they?  Here's where it gets complicated. 

Assuming Hillary or Barack win (we should be consistent- either both first names or both last names), they will certainly nominate far left wacko judges.  BUT... John McCain could very well be back in the Senate, having two years left on his term.  If he holds his "gang of 14" together, a Republican minority could filibuster the nominee(s), just as McCain said would be necessary.  If the Democrats, as is their nature, decide to break their promise and change the rules (as Republicans tried to do but McCain prevented) to prohibit filibusters of judges, then those liberal judges win and conservatism loses.   Big time.  For a long time. 

If, on the other hand, there is a Republican majority (including McCain) in the Senate, they don't need a filibuster, they can simply refuse the nomination.  But will McCain accept that or side with Hillary?  His track record would suggest he holds a grudge at conservatives, and losing the Presidency would be a big grudge-maker, so he might. 

OK, suppose McCain manages to win.  Will he appoint conservative judges, as he has promised?  Certainly they should be more conservative than the alternative.  But if McCain gives up his Senate seat and Democrats keep the majority (the "gang of 13" stays together), they will certainly block his nominees.  Irony and justice, perhaps, but not helpful to the conservative cause. 

If, somehow, Republicans gain the Senate majority without McCain's Arizona seat (mind you, the Governor there is a Democrat), the Democrats can still use the "gang of 14 rule" to filibuster and stop his nominees.  More unhelpful irony and justice.  And this is the best-case scenario, thanks to John McCain!  The only thing better would be for Republicans to break the gang of 13 and McCain's Senate legacy, and change the rule.    

Let's sum up:  Of the four possible combinations of President and Senate, one is better than nothing, thanks to John McCain; one is barely tolerable, depending on John McCain; one is not so good, thanks to John McCain; and the best of the lot would have to be in spite of John McCain. Sometimes, Senator, the universe wraps around and bites you in the Democrat.