by Nicholas Beaudrot of Electoral Math
I'll have more to say on the topic of coattails later, but for the moment, let me mention the conditions under which the results at the Senate or Presidential level don't have much impact on House races.
In states with only a single, at-large House member, the results of the Presidential and Senate races have virtually no impact. Presumably, this is because their is enough media coverage of the two or three races that voters can consider more independently than voters in, say, the New York City media market. In addition, a small number of "freak of nature" politicians have little or no impact on House races. Democratic Senators in Nebraska, for instance, or Republican Senators in Rhode Island, cannot convince their voters to punch a straight-ticket ballot.
The punchline for this year is that Jon Tester (D) will probably be unable to drag Monica Lindeen (D) to victory in Montana. But, it also means that Senator Craig Thomas's (R) campaign will have little impact on Gary Trauner's (D) bit for a House seat in Wyoming.
