David Plouffe, in an interview with NY Times Magazine's Robert Draper:
Beating the Clintons [in 2008], that was, in terms of scale of difficulty, significantly above beating Romney.
You can read that as either praise of Clinton's strength or ridicule of Romney's weakness, since after all the two aren't necessarily in opposition. But something tells me Plouffe meant the latter.
It's indisputable that Obama ran a brilliant campaign--one for the history books. Yet I expect the comprehensive histories, in detailing Obama's victory, will devote not equal but more space to Romney's ineffable bumbling: his failures to read the national mood, to appreciate disagreeable polling, to recognize his own fatally flawed themes, and to exploit new campaign technologies, which is the thrust of Draper's lengthy piece, "Can the Republicans Be Saved From Obsolescence?"