An interesting statistic about the Daschle-Thune race:

Mr. Daschle and his Republican challenger, former Representative John Thune, will have spent nearly $30 million - roughly $40 per capita in the mainly rural state - by the time the race is over.

$40 per capita! I don't know the exact numbers, but in the past year and a half of presidential campaigning (including the Democratic primaries), I'd guess the candidates' spending totaled $700-$800 million, or about one-twentieth of the per capita spending on the South Dakota Senate race.