Really only two predictions here.
1) The Democrats will maintain (relatively) comfortable control of the Senate. They’ll only lose (net) a couple of seats.
2) The Democrats will maintain control of the House, but it’s going to be a lot tighter. What they’re going to lose mostly is Blue Dogs, so ironically the House activity will be more to the left despite the narrower majority.
That last begs a bit of expansion. What the house acts upon comes from committees. Fewer blue dogs in total means fewer in committee and sub-committee leadership positions.
As to the control issue, Cook rates 31 seats as tossups. Assume for just a moment that the Republicans win every single one of them plus the six presently Dem seats that Cook rates as lean or likely Republican, and the Republicans still do not win control of the house. They have to also pick up some seats Cook rates as leaning or likely democratic. In other words, some upsets. And that’s if you trust Cook’s numbers.
Cook rates Hawaii’s district 1, presently held by a Republican, as a tossup. Really, a toss up. He got less than 40% in a three-way fight. In November, he’ll be duking it out with just one Dem, in a district that’s been more than +10 Dem for literally decades including in 2008.
That race being coded as a toss up calls every one of Cooks’s other calls into question.
I think given the current situation the Republicans could pick up as much as 2/3 of the total tossup. As already noted, that’s not enough to take the house.