A good article states that calling new witnesses is unconstitutional.
I’m with you. But here is the genius of Mitch McConnell: He has given the handful of reluctant GOP Senators ample cover when he agreed to have a vote at the end for “more witnesses” After the case presentation, after the Q & A sessions...
In that way, he can get his 50 votes and still allow a Senator or two on the fence to claim she came to her decision after finally deciding that A) the articles from the House do not rise to the level of High Crimes and Misdemeanor , B) No amount of new witnesses will change that or the final disposition and C) She is grateful that the Majority Leader agreed to time for this body to consider the possibility which is all she wanted in the first place.
It is unconstitutional, but then the House impeachment did the follow procedure and should have been thrown out. This is politics and the laws that we the PEOPLE have to follow go out the window.