James Joyner puts the Republican field in perspective:

In December 2007, few of us thought that Barack Obama had the gravitas to be elected president.  Ditto George W. Bush in December 1999. [Much less a year earlier in both cases -- the more apt comparison!]

And, as Nyhan reminds us, there were all manner of reports in late 1991 and early 1992 lampooning the “Seven Dwarfs” who were vying for the Democratic nomination and the opportunity to get trounced by the popular incumbent George H.W. Bush.  By the spring they seemed destined to nominate some boob from Arkansas who was “damaged goods” and “who lacks the trust and affection of a majority of Democrats, not to mention the independents vital for victory.”  But, as some may recall, Bill Clinton went on to not only beat Bush easily but clobber Bob Dole to win a second term.