If McCain were to jump ship and endorse a candidate from the other party (as his friend and former 2000 Democratic vice presidential nominee, Joe Lieberman did in 2008, it would be a big deal. McCain was, after all, the 2008 nominee.

But the larger problem would be that McCain might represent a larger bloc of neoconservatives and internationalists who make up a sizable portion of the Republican coalition — especially at the opinion leader level.

Of course, even if Paul were to win the nomination, this theory assumes he wouldn’t make efforts to build bridges or balance the ticket. The younger Paul (who just endorsed Mitch McConnell for re-election) has proven rather adept at politics.