“If you believe that Clinton retains advantage in the presidential race and I’m still in that camp then I think by extension you have to also believe that Democrats are better than 50-50 to take back the Senate,” said Kyle Kondik, a political handicapper at the University of Virginia Center for Politics.

The GOP is at a disadvantage because it has to defend 24 seats while Democrats only have to protect 10. Democrats need a net gain of four seats and control of the White House to take back the Senate majority.

Of the ten Senate seats most likely to flip, nine are currently held by Republicans and only one by a Democrat: Sen. Harry Reid (Nev.), the minority leader who will retire at year’s end.

For Republicans to keep control of the Senate, their candidates will have to run well ahead of Trump in states that President Obama carried in 2008 and 2012. That’s tough for Senate candidates to do by more than a few percentage points.