historically
toss ups go to the anti incumbent 75%
this is going to be an election for the ages
I saw this over at NRO just now, looking at some analysis by Cook and Rothenberg predicting a 57 House seat pickup for the GOP:
What about the toss-ups? They break only slightly toward the winning party. In 2008, Cook rated 35 races as toss-ups; Democrats won 19 of them, or 54 percent. In 2006, he rated 39 races as toss-ups; Democrats won 22 of them, or 56 percent.Rothenberg’s ratings are more complicated, but obtain nearly similar results. In 2008, he said 14 races were pure toss-ups; Democrats won seven of them. Democrats won nine of the 13 races labeled as tilting Democratic, and Republicans won all of toss-ups tilting their way. All together, Democrats won exactly half of the 32 toss-ups. In 2006, Democrats won ten of the 19 pure toss-ups, all of the races that were tilting Democratic, and one of the ten tilting Republican. Combine all the toss-ups and Democrats won 21 of 40, or 52.5 percent.
This makes sense to me, and is closer to the 50-50 tossup split that I figured. I don't know why you think to-ups go 75% for the anti-incumbent. It's just not true.