A string of races where polls close at 8 p.m. ET on Tuesday will likely play a massive role in the fight for control of the Senate and House.

Follow the most up to date results for key races here.

Results in key races will start coming in after 6 p.m. ET, and Democrats' fortunes in early reporting states will give some clues into how successful they can be in red territory in this year's midterm elections. The results that will come in after 8 p.m., though, will make or break Democrats' chances of taking control of Congress.

The contests will determine whether one of the most vulnerable Senate Democrats can win re-election — or if the party can pull upsets in two of the only states where it has a chance to win a GOP-held seat. Meanwhile, Democrats could all but wrap up a House majority — or come closer to failure in reaching their goal of flipping a net 23 GOP-held seats — in races across Pennsylvania, New Jersey and several Midwestern states.

Here are the key races to watch at 8 p.m. ET: