A somewhat higher threshold for viability is one based on fundraising numbers. For instance, in how many districts have both the Republican and Democratic candidates raised at least $100,000 in individual contributions? While $100,000 is not enough to run a full-fledged campaign for the Congress, it’s at least enough to get a candidate on the map in all but the most expensive districts.

The answer — as of the July 15 filing deadline (a fresh set of fundraising numbers will be available in about a week) — is 163 districts. This number represents a big increase from past years: there were 116 such districts at a comparable point in the election in 2008, for instance, and 102 in 2006 — and an average of 77 from 1998 until 2004. Although fundraising has become easier because of the Internet and other means, and although the rate of campaign contributions has been increasing much faster than inflation, this is nevertheless an impressive figure…

Why are so many races competitive? That could merit an article on its own. I suspect much of the reason is that the deterioration in the political environment for Democrats was evident quite early in the cycle — certainly by around August or September of last year — leaving both parties with plenty of time to prepare. The fact that the Internet has made fundraising much less burdensome, and allowed name recognition to be built through a variety of “nontraditional” means, may also play a role.