GOP Senate Majority May Be in Peril

The general thinking about the Republican Senate majority is that it has solidified to the point where Democrats are effectively shut out of gaining control of the upper chamber in 2020. But in truth, the GOP majority is in more danger than many analysts believe. Just how much jeopardy depends on how you think about the overall state of the race: If the election is going to be close, as many analysts (including myself) seem to believe, then the Senate probably leans Republican at best. And if President Trump is likely to lose, perhaps badly (as other analysts suggest), then Republicans will have a very difficult time maintaining control of the chamber.
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The bad news for the GOP is that most of the competitive seats are held by Republicans. It is still early, and the list could change if, say, Democratic Gov. (and presidential candidate) Steve Bullock switches over to the Senate race in Montana, or former Arkansas Gov. Mike Beebe gets into the Senate race there. But for now, Democratic seats in Alabama, Michigan, Minnesota and New Hampshire are considered potentially competitive, while Republican seats in Arizona, Colorado, Georgia, Iowa, Kentucky, Maine, North Carolina, and Texas have varying degrees of competitiveness.
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Looking at individual seats, we see that Republicans would not be favored to be competitive in races for any Democratic-held seats except Alabama’s, which reflects conventional wisdom. If the remaining seats did not flip in the good GOP year of 2014, it is difficult to see them flipping if a Republican president’s job approval is at 42.5 percent.

Republicans start out as underdogs in Maine and Colorado. This probably overstates Susan Collins’ vulnerability, in the same way the simulations overstated Joe Manchin’s vulnerability in 2018. On the other hand, Manchin came within three percentage points of losing his race, though his state is substantially more Republican than Maine is Democratic.

In any event, the key battlegrounds are shaping up to be Arizona, Georgia, and North Carolina, with outside Democratic chances in Iowa, Kentucky, and Texas.