During the impeachment trial, Trump has packed his schedule with the announcement of his long-awaited Middle East peace plan, the signing of a trade agreement between Mexico and Canada, campaign rallies and visits of foreign leaders.

White House aides said they were satisfied with the Trump team's opening statements, particularly singling out remarks late Monday by Alan Dershowitz, who argued among other things that the claims in Bolton’s unpublished book — if true — wouldn’t constitute an impeachable defense.

“Professor Dershowitz made it very clear last night even if everything that came out in the New York Times article were true, there would not be an impeachable offense and I think the basic principle remains that it is not the role of the Senate now to begin taking new witnesses when the House didn’t even seek a subpoena,” an official on the president’s legal team told reporters. “That would fundamentally change the relationship between the House and Senate in this kind of proceeding.”

After the Bolton manuscript story emerged, aides initially feared many Republican senators calling for witnesses, a separate White House official involved in the impeachment process said in an interview. But “even with all the new Bolton stuff that came out, you didn’t see a huge sea change“ in senators’ opinions.

Trump has hinted more than once that he would invoke executive privilege — the protection for the president’s ability to receive confidential advice and to trade views freely with his advisers — if the Senate tries to call his former or current top aides, including Bolton and acting White House Chief of Staff Mick Mulvaney.

“You could call it a presidential prerogative,” Trump told reporters last week during his trip to Davos, Switzerland. “The way I look at it, I call it national security. Executive privilege, they say. So John would certainly fit into that. When you’re a national security adviser ... I just think it’s very hard.”

Deputy White House Counsel Patrick Philbin told senators that the Supreme Court has recognized that the “confidentiality of communications ... is fundamental to the operation of government,” he said. “This is a standard principle asserted by the administration of both parties. It is not a partisan issue."

No decision has been made but if Trump invokes executive privilege , Supreme Court Chief Justice John Roberts, who is presiding over the trial, could rule, subject to an appeal to the full Senate. But Trump could try to take the dispute to court, filing a motion to quash the subpoenas in U.S. District Court in Washington, which could eventually end up before the full Supreme Court.

“There are the legal implications for members to consider including questions of executive privilege,” said a senior GOP aide. “I don’t know how much patience there is amongst the senators to be waiting around.”