Having an incumbent Presidential election normally results in many more voters of that party voting than in mid-terms. This also means more down ballot votes for House and Senate elections of the Presidential party. In general this would suggest Republican Senate and House incumbents and challengers have an advantage in the upcoming elections. The thing that is working against Republican Senate is that they have to defend twice as many seats as the Democrats. So I wouldn’t be surprised if Democrats gain a few seats in the Senate. It is probably going to remain a nearly evenly split Senate. On the bright side, the House could swing a bunch towards Republicans. If we are lucky, Trump will get a near blowout, as that could lead to a much rosier scenario than the above.