I get asked pretty often whether enough R Senators might get arrested to get a majority to vote out Trump. Prob not. The Constitution prevents the executive branch from arresting legislators to keep them from debating or voting. Thats the "SPEACH AND DEBATE" clause.
Constitution: “[Congress] shall in all Cases, except Treason, Felony and Breach of the Peace, be privileged from Arrest during their Attendance at the Session of their respective Houses, and in going to and returning from the same...."
So ... Congressmen and women enjoy a lot of protection. It's not unlimited, but you can imagine that the FBI/DOJ would be VERY hesitant to intrude on an impeachment vote in Congress. Based on that, my guess is that all the sitting Senators will be voting.
