Trump impeachment trial live updates: Biden says charge 'not in dispute' in 1st comments on acquittal

Bruce Castor told reporters that he thought Trump's legal defense had a "good day," though other members of the defense team and Republican senators were less enthusiastic.

David Schoen, who followed Castor on the Senate floor, was not so sure of his performance. When asked by reporters how he thought the senators responded to the arguments, he said he "didn't know what they thought." And after learning about criticism from Sen. Bill Cassidy, R-La., Schoen added that he was "sorry he felt that way."

Schoen also responded to a question asking if it meant anything that another Republican the voted with the Democrats on the question about the constitutionality of the proceedings.

"I don't think so. I don't really follow that stuff so carefully, but I was very heartened by some of the comments I got from some of the people. I think they all just vote their conscience, I guess," Schoen said. "They vote how they think best, I guess."

Sens. Susan Collins, R-Maine, and Lisa Murkowski, R-Alaska, who both voted as they did previously on the question, said they were "perplexed" and "stunned" by Castor's presentation. 

 "I thought the first attorney for the president today did not present a case -- which surprised me -- did not make any arguments. The second attorney that represented the president clearly did and did a competent job but I am puzzled by the presentation by the first attorney," Collins said. "So I don't know how they are going to proceed from here on out."

Murkowski said, "I was really stunned at the first attorney who presented for former President Trump. I couldn't figure out where he was going, spent 45 minutes going somewhere, but I don't think he helped with us better understanding where he was coming from on the constitutionality of this."

"And I felt that Mr. Schoen did a, did a better job but I think they sure had a missed opportunity with their first, first attorney there," she added.

-ABC News' Allison Pecorin and Trish Turner

As Trump was tracking the impeachment trial from Mar-a-Lago, his Florida resort, he was not pleased with the performance of his defense team and specifically Bruce Castor, sources familiar with the matter told ABC News. 

Anticipating Trump’s eventual reaction, people close to the former president tried to keep his focus elsewhere, sources said, but he was watching portions of it. 

Trump had been bracing for a defense much less successful than his defense team during his first impeachment trial, but at times he was stunned to hear some of the arguments, specifically how Castor complimented the presentation by the Democrats, sources said.

-ABC News' Katherine Faulders and John Santucci 

Following the first full day of the Senate's first impeachment trial of a former president, Senate Majority Leader Chuck Schumer praised the performance of lead House impeachment manager Rep. Jamie Raskin, D-Md.

"I thought that manager Raskin’s argument was one of the most powerful I’ve ever seen. He hit it out of the park. It was both erudite and touching. It really -- it really got to your heart," Schumer said.

The trial resumes on Wednesday at noon with House managers making their opening arguments on the charge of "incitement of insurrection."

Sen. Bill Cassidy, R-La., told reporters on Capitol Hill Tuesday night that he voted that the trial was constitutional because of the "compelling argument" by the House managers.

"I always said, I would be an impartial juror, anyone that listened to those arguments would recognize that the House managers are focused, organized -- they relied both upon precedent, the Constitution and legal scholars," Cassidy said. "They made a compelling argument. President Trump’s team was disorganized, they did everything they could but to talk about the question at hand."

However, Cassidy stressed that he still is not sure how he will vote for conviction of the former president, repeating that he is an "impartial juror."

-ABC News' Trish Turner