“Are you ready?” Pelosi asked her colleagues, after describing constitutional circumstances posed by Trump’s alleged abuse of power surrounding his Ukraine dealings, as well as his subsequent decision to stonewall the House investigation into the matter.

The caucus, according to multiple members who attended, erupted with shouts of approval.

While Senate Republicans prepare to aggressively defend Trump in the trial that would follow a vote to impeach in the House, the details of how the proceeding will be conducted still need to be worked out.

The White House officials who met with GOP senators Wednesday offered few specifics of how they would like the trial to be structured and what witnesses should be called, according to senators, even as they repeatedly stressed why they believed the impeachment developments in the House were flawed.