Democratic spin doctors have set out how their side is going to hold onto a majority in the House. They'll capture four at-risk Republican seats, hold half of the next 30 or so Democratic at-risk seats, and avoid significant losses on target seats lower on the list.

That's one plausible scenario. The shift of opinion away from Democrats so evident in the polls could turn out to be illusory. The widely held assumption that Republicans will turn out in greater numbers than Democrats could prove wrong.

Democratic candidates do indeed have a money advantage in many close races, and their campaign committee has more cash than its Republican counterpart...