Why do parties nominate bad presidential candidates?

I've been thinking a lot about the right's complaint that Romney's a bad candidate, or as Joe Scarborough put it yesterday, "a terrible politician."

OK, Romney's obviously not that great at retail politics. So how did he mop the floor with the other candidates in the GOP primary? And why, if he's so awful, did he finish second in 2008?

The answer is pretty obvious: the Republican Party is a mess -- much like the Democratic Party was in 1984. Walter Mondale emerged from a weak field that included Jesse Jackson, Tom Eagleton--and George McGovern--who managed to win a whopping one state against Nixon in 1972.

The point is: the Democratic field wasn't weak because Democrats just got unlucky that year. It was weak because the party had become self-indulgent, intellectually lazy and too insular to see that America in 1984 wasn't clamoring for a return to the Carter Administration. Mondale didn't break with Carter in any significant way that I recall, checked all the right liberal boxes -- and that was good enough for the party.

Similarly, the GOP is too tightly ensconced in their right-wing cocoon to see that America doesn't pine for a return to the Bush administration. Romney wasn't W's vice president, but he's endorsing all the same policies, never repudiated the Bush years, checked all the correct right-wing boxes during the campaign -- and that's was good enough for Republicans.

While it's true that bad candidates can hamper strong parties (Adlai Stevenson comes to mind), it's usually the case that crappy parties produce crappy candidates.