Trump adviser Jason Miller has walked back and forth on Capitol Hill with a stack of papers he says is a witness list and has 301 names -- "SO FAR," the top page reads.

He told ABC News he’s not ready to share the whole thing yet because it’s a work in progress, but it signals Trump's team will match Democrats' call to have witnesses by potentially inundating the trial with them.

Miller's pacing comes as Republican Sen. Lindsey Graham has doubled down on his call for multiple witnesses -- if any are ultimately called with the resolution.

"It is my firm belief that the House Managers are trying to investigate the case AFTER it was brought to the Senate. It is better for the country to go to a final vote," Graham tweeted. "However, if the body wants witnesses, I am going to insist we have multiple witnesses."

Graham said the Senate could start with House Speaker Nancy Pelosi -- a sentiment floated by Trump defense attorney Michael van der Veen on the floor Saturday when he called for the trial to end "today."

The scramble for party leaders to work on a trial resolution for witnesses comes after the unexpected vote and call from House managers to subpoena Republican Rep. Jaime Herrera Beutler, who has said she has information on an intense call House Minority Leader Kevin McCarthy had with Trump during the Capitol attack, in which Trump sided with the mob while violence was underway.

-ABC News' Katherine Faulders and Allison Pecorin

After the Senate moved in a 55-45 vote to consider a resolution to call specific witnesses, Senate leaders are now meeting to draft that resolution.

According to sources, it should contain specific information on how the trial will move forward.

The resolution will be amendable, which means Republicans could offer endless amendments. Each amendment would get two hours of debate before a vote. Many want to avoid that situation, according to sources.

Sen. Chris Murphy, D-Conn., told ABC News the House managers could still decide to call no witnesses. In the end, the Senate will need to vote again on the resolution, which requires a simple majority vote to pass.

Lawmakers have begun to go back to their office building, so it appears the trial is in a holding pattern for some time.

-ABC News' Trish Turner

The Senate has called a recess until 12:30 p.m. as Senate leaders draft a resolution to call for witnesses in Trump's trial, following a 55-45 vote.

According to sources, the resolution -- which the Senate will need to vote on -- should contain specific information on how the trial will move forward.

Senators on both sides of the aisle seemed surprised by House impeachment managers' move to call for witnesses Saturday, according to pool reporters inside the chamber.

Sen. Ron Johnson, R-Wis., turned to Sen. Mitt Romney, R-Utah., at one point and was visibly upset with him, even pointing at him once. The two went back and forth with Sen. Dan Sullivan, R-Alaska, in the middle of them.

Johnson said, "We should've just ended this, that's all I'm saying," and told Romney, "Blame you."

Romney was the only Republican to vote to convict Trump at his last impeachment trial.

When lead House impeachment manager Rep. Jamie Raskin, D-Md., raised bringing in Rep. Jamie Hererra Beutler, D-Wash., as a witness, Sen. Lindsey Graham, R-S.C., shook his head no and put his head down on his hand on his forehead.

Graham later joined four Republicans --Sens. Mitt Romney, Susan Collins, Lisa Murkowski and Ben Sasse -- in voting to hear witnesses after threatening to delay the trial with witnesses of his own.