It’s become difficult to get a sense for the state of play in Congressional races. Polling tends to be fuzzy at that level under the best of circumstances. Trump is making that task even more challenging by scrambling the normal assumptions about the relationship between top/down-ballot voter behavior.
How many traditional Republican voters will split their votes between a Trump alternative and the Republicans farther down the ballot? How many of them will just stay home? It looks like we are seeing an unprecedented surge in turnout among Democratic constituencies. Are we going to get an outcome more like ’06 and ’08? Will this surge be large enough to threaten Republicans who hold strong leads in the polls, like McCain and Rubio?
Democrats are certain to take the Senate, but they would need an enormous wave to gain the 30 seats they need to take the majority in Congress. The Cook Political Report is the best comprehensive look at those races. They are a consistently cautious source and they still rate that possibility as unlikely. However, when you look at some of the races they are hedging on, you can see how a wave election might potentially produce the swing Democrats are hoping for.
Cook rates IL-10, Bob Dold’s district, as a Republican-leaning tossup. That’s pretty absurd. Races there tend to be close, but that seat goes pretty strongly Democratic in Presidential years and Republican (by a few hundred votes) in strong Republican off-years. Dold has no shot and he’s pretty much known it since he (re)won the seat in 2014.
In California, Cook rated Darrell Issa as a likely win for months despite evidence to the contrary. They finally downgraded him recently. Every California Republican in Cook’s “lean” category should probably be sweating right now.
In the last few Presidential elections voters’ preferences for President correlated pretty closely with their down-ballot voting. However, a few decades ago ticket-splitting was common. As the GOP disintegrates at the national level we may see a return to that pattern. My guess, however, is that we will only see this in off-year elections. People turning out in droves over their disgust with Donald Trump are not likely to spare Republican Congressional candidates from their anger.
It is impossible to tell whether Democrats will gain enough seats to retake Congress, but you can bet that Republican Senate and Congressional candidates who failed to aggressively distance themselves from Trump are going to underperform their current poll numbers by several points on Election Day. Trump has transformed what was otherwise going to be a modest Republican loss this year into an historic rout. This is exactly the kind of wave election Democrats were hoping for.