Americans head to the polls for elections that could define Trump's closing chapter

Winning the Senate on Tuesday is likely to be a much harder task for Democrats.

Thirty-five seats are up for election, and they will need a net gain of four to win control. If they lose in Michigan - a battleground seat they already hold - they will need a net gain of five seats to win it.

Most of the battleground races are close and several sit within the margin of error for pollsters. The crucial Senate races to watch are in Michigan, Texas, Ohio, Iowa, Maine, Alaska and North Carolina.

This is, in reality, where these midterm elections will be won and lost.