Not normally given to praising Karl Rove, I find that he makes an important point that I’ve emphasized myself:

In the primaries, Mr. Obama instead moved hordes of volunteers from state to state. It was a brilliant tactic, but Nov. 4 is different. The volunteers adequate for primaries held over five months will simply not be enough to compete in 51 separate elections (all 50 states plus the District of Columbia) all on one day.

Many people (including some conservatives), impressed by what Team Obama accomplished in the Democratic nomination campaign, seem to assume that the same methods will automatically translate to victory in the general election. But the challenges of a general election are in several ways fundamentally different from a primary campaign. This is not the Iowa caucuses.