As House managers argue intensely about the need to hear from key witnesses at the Senate trial, a source familiar with the process tells CNN that the President’s allies are already working hard behind the scenes to lobby wavering GOP senators to oppose any witnesses.
This effort includes calls from members of the President’s team and allies on Capitol Hill. They're also identifying people that the senators trust and respect from a wide variety of places, including back home, and getting them to call.
The specific arguments against witnesses vary depending on who the senator is and what their concerns are, CNN is told.
Remember: 51 senators would need to vote to have witnesses at trial. If all 47 senators who caucus with the Democrats vote to have witnesses, they still need four Republicans to join them.