Given how splintered politically we are as a country, I doubt it would have a huge impact on Congressional races. As it is, it remains to be seen if a re-elected Trump would have any coattails.
There are two kinds of coat-tails:
—The commonly publicized positive coat-tails, where voters switch parties to the Presidential candidate and vote the Presidential candidate’s party line
—The mostly ignored negative coat-tails, where voters refuse to show up to the polls because they dislike the Presidential candidate, so they are not available to vote the Presidential candidate’s party line
It is the _negative_ coat tails that would sink the Democratic down-ticket candidates.
In the 30 congressional districts that Trump won that are currently held by the Democrats? You bet.