Senate and house of reps are getting new seats. 435 in House of Representatives and 34 in Senate. They are predicted to stay in republican favor. This maters when it comes to veto and overriding power. I think that if you have a democratic president and a republican majority vote the president won't have as much power and it'll be more of what the people want. It also will work the other way around, but if there is a republican president and republican popular vote the president will have more power.