I had fun giving Bob Mercer heck for his purely speculative September hypothesis that the folks who voted for B. Thomas Marking in 2010 decided that election and could have decided this year's House race. I long maintained that there was no evidence that Marking had any influence on the 2010 outcome and that it thus made no sense to assume those folks would do anything other than split evenly this year between Kristi Noem and Matt Varilek.

But then I looked at a few simple numbers that indicated I was wrong—not as wrong as Bob Mercer, mind you, but wrong on the neutrality of the 2010 Marking vote. Consider:

  1. In 2010, B. Thomas Marking won 19,134 votes for Congress, 6.0% of the votes cast in that race.
  2. Marking's percentages in each county correlated weakly but significantly (r = 0.3596, p = 0.003) to Noem's 2010 county percentages. Where Noem was strong, Marking tended to have a little more strength than his average as well.
  3. Marking's percentages correlated a bit more strongly and negatively (r = –0.4583, p = 0.0001) to Stephanie Herseth Sandlin's. Where SHS was strong, Marking was noticeably weaker.
  4. This year, Matt Varilek's percentages in each county correlated negatively (r = –0.3899, p = 0.001) to Marking's 2010 numbers in each county.

In other words, these data suggest that, if the Marking 6% were anything other than statistical error in 2010, they were stronger in places where Noem was already stronger than SHS in 2010. An exact percentage is beyond this morning's math, but these numbers lead me to believe that Marking voters did not siphon equal numbers of voters from the party candidates in 2010. Marking more likely dragged down Noem more than SHS. Had he not run, his voters would have leaned significantly toward Noem.

And this year, that tendency held. Noem beat Varilek by 53,851 votes, 14.9% of the electorate. But I'm willing to be that a strong majority of Marking's 6% added to Noem's cushion.