The Senate impeachment trial of President Donald Trump is expected on Friday to vote on the pivotal question of whether to allow additional witnesses and documents as evidence. And with Senate Majority Leader Mitch McConnell’s recent comments to his Republican conference that he doesn’t yet have the votes to block the move and that his party members should unify in opposition to it, the decision could hang on the votes of a handful of Republican senators. At the beginning of the trial, the Senate decided it would vote on additional evidence after lawmakers completed their 16 hours of written questions for both President Trump’s attorneys and the House managers prosecuting the case.