The battle for the Senate majority in 2020 was always going to be heated. And now here comes impeachment.

The Senate’s impeachment trial of President Donald Trump is stuck in limbo, but the looming verdict will likely be the most consequential vote senators take before next year’s elections — and a weighty position for challengers seeking to join the chamber.

Impeachment also threatens to yoke the 35 Senate races even closer to the presidential contest. The politics around impeachment have calcified for both parties, with public opinion rigidly consistent and senators and candidates mostly falling along party lines ahead of a prospective vote on whether to acquit Trump or remove him from office.

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Democrats — who need to net three seats in next year’s elections to win control of the chamber if they also win the presidency — have attempted to squeeze vulnerable GOP senators, calling for a fair trial to include administration witnesses who refused to testify before the House and criticizing Majority Leader Mitch McConnell for saying he does not consider himself an impartial juror.

But Republican senators have shown few signs of breaking with Trump — instead criticizing House Democrats’ impeachment process as sloppy, partisan and incomplete — following a similar pattern after not a single Republican defected from Trump in the House.