Democrats have to hold 25 Senate seats next summer... We'll see how brazen they are in 6-9 months. My guess is the GOP will not get above 63-65. The GOP could hit 60, but I think probably 55-45/57-43...
History tells us that usually the minority party does much better the midterm election after the minority party lost the Presidency the last election. We saw a massive wave of House Republicans in 2010 led by Kantor and Ryan, followed by big time Senatorial wins in 2014. Think the Democrats will be much better motivated after 1 1/2 years of Trump, and I think the Alabama win, albeit short term, will try to give them a blueprint for Summer 2018. I don't think we're going to see the GOP run up the Congressional scoreboard, but I think picking up another 3-5 seats is a realistic goal. The Democrats are still being run by a small but powerful flaming far left liberal group who is not going to get that party back to Bill Clinton era dominance. On top of that, TAX REFORM will give the GOP a MASSIVE amount of goodwill with the public... A lot can happen though between now and next summer, but tax reform and a potential bi-partisan infrastructure bill would be big for the GOP.