From today's WaPo Editorial page:

While a host of issues were at play in this election, the primary reason John McCain lost was the substantial erosion of support from self-identified moderates compared with four years ago. In 2004, Democratic nominee John Kerry held just a nine-percentage-point margin among moderate voters over President Bush. This year, the spread between Barack Obama and McCain was 21 points among this group. The net difference between the two elections is a deficit of nearly 6.4 million moderate votes for the Republicans in 2008.

This is a good analysis by a consistently critical Republican of the hard right bend in the current party.