(CNN) Former President Donald Trump was unhappy with his impeachment lawyer Bruce Castor's opening argument on the Senate floor Tuesday, two people familiar with his reaction told CNN.

Castor, who is representing Trump alongside attorney David Schoen, delivered a meandering argument during the first day of the Senate impeachment trial, including praise for the House impeachment managers for a presentation that he said was "well done."

Trump was almost screaming as Castor struggled to get at the heart of his defense team's argument, which is supposed to be over the constitutionality of holding a trial for a president no longer in office. Given that the legal team was assembled a little over a week ago, it went as expected, one of the sources told CNN.

Still, Trump's allies were flabbergasted when the attorneys switched speaking slots at the last minute.

Castor's discursive presentation featured lengthy praise of the Senate, including his home state Pennsylvania senators -- Republican Pat Toomey and Democrat Bob Casey -- while arguing that the Senate should not be holding the trial. He warned that a second impeachment trial in 13 months would "open the floodgates" to future impeachments, even making the unfounded rhetorical suggestion that former Obama administration Attorney General Eric Holder could be impeached.

The Senate ultimately voted 56-44 that the impeachment trial is constitutional.

An adviser to Trump's team offered a candid assessment of the messy opening day, asking pointedly, "What the hell is going on?"

The adviser said the former President could be in serious jeopardy if he finds himself charged in criminal court, given his inability to attract a high-powered legal team for the impeachment trial.

"Trump is f--ked if anyone ever charges him. No one wants to work with him," the adviser said.

Schoen was supposed to present first, not Castor, two people familiar with the plan told CNN. But Castor told the Senate that Trump's legal team "changed what we were going to do on account that we thought that the House managers' presentation was well done."

After Castor yielded to Schoen, the tone of the defense team changed starkly. Schoen charged that Democrats were using impeachment as a political "blood sport" to try to keep Trump from running for office again, accusing them of trying to disenfranchise pro-Trump voters.

Though the former President was displeased by his defense team's early performance, his staff remained confident that he was headed for acquittal and it would not change the outcome of the trial. Two separate sources close to Trump say he's lying low through the end of the trial but talking with aides about how to reemerge and help Republicans around the midterm elections.

A separate senior adviser to Trump insisted that Castor was attempting to lower the emotional temperature in the Senate before Schoen began his presentation.

"This is about lowering the temperature following the Democrats' emotionally charged opening, before dropping the hammer on the unconstitutional nature of this impeachment witch hunt," the adviser said.

But even some GOP senators signaled they were unimpressed with the presentation.

Republican Sen. John Cornyn of Texas -- who nonetheless voted that the trial was unconstitutional -- told reporters bluntly, "I thought the President's lawyer -- the first lawyer -- just rambled on and on and on and didn't really address the constitutional argument."

"Finally the second lawyer got around to it, and, I thought, did an effective job." He quickly added, "But I've seen a lot of lawyers and a lot of arguments and that was -- it was not one of the finest I've seen."

Republican Sen. Bill Cassidy of Louisiana, who was the only senator to vote differently than in a procedural vote last month on the constitutionality of the trial, told reporters that the "House managers were focused, they were organized" and "made a compelling argument," while in contrast, "President Trump's team were disorganized."

"They did everything they could but to talk about the question at hand, and when they talked about it they kind of glided over, almost as if they were embarrassed of their arguments," Cassidy said.

Republican Sen. Lisa Murkowski of Alaska similarly said: "Today was supposed to be an opportunity to, to be briefed on the constitutionality of whether or not you can move forward with an impeachment of a former president."

"I thought that -- that the House presented a pretty good, pretty good legal analysis. In fairness, 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," Murkowski said.

A source who advised the Trump campaign said plainly, "Getting criticized by both sides. Yikes."

Castor and Schoen, each of whom has a history of being involved in controversial legal matters, were tapped to lead Trump's legal team one day after CNN first reported that five members of his defense had left abruptly. One point of friction with his previous team was that Trump wanted the attorneys to focus on his election fraud claims rather than the constitutionality of convicting a former president.

A source close to the first Trump impeachment team said the former President's current lawyer shouldn't be compared with the attorneys who represented him at his first trial.

"It is hard to compare to our team," the source said of Trump's first impeachment team, noting it featured the likes of Bill Clinton impeachment veteran Judge Ken Starr, Harvard professor Alan Dershowitz and former Florida Attorney General Pam Bondi. "Different level of experience."

Despite the criticism, Castor simply told reporters after the day's session: "I thought we had a good day, thank you."

Source: CNN