Seth Masket posts the above chart from The Party Decides:

[T]he longer a party is deprived control of the White House, the more moderate its presidential nominees become. One term out of office may be a fluke, but two terms is serious, and three is catastrophic. Parties take this seriously and tend to nominate considerably more centrist people, sacrificing a significant chunk of their governing agenda for a chance of actually governing.

That assumes a party hasn’t jumped the shark and become a populist-religious movement more concerned with purity than power. But maybe that’s just part of a transitory phase as well. But here’s hoping we have a credible GOP by the time the Obama wave subsides. A country needs two sane parties, not just one.