WASHINGTON — The impeachment trial of President Trump, expected to open Thursday in the Senate, is shining an intense spotlight on a handful of Senate Republicans who hold the power to decide a key question: whether to call witnesses.

On one end, a group of influential swing GOP senators — Susan Collins of Maine, Lisa Murkowski of Alaska, Mitt Romney of Utah, and Lamar Alexander of Tennessee — are pushing to hold a vote on whether to call witnesses later in the proceedings.

Democrats have vowed to exert pressure on the group to break with their party on witnesses and other issues, such as obtaining documents.


At the same time, the Senate’s right flank is increasingly making the case to majority leader Mitch McConnel of Kentucky and other GOP leaders for a more aggressive posture in defense of Trump. In a private meeting with McConnell on Tuesday, Texas Senator Ted Cruz argued that if Democrats press the case for potentially damaging witnesses — such as former national security adviser John Bolton — the GOP should insist on incendiary witnesses of their own, such as Hunter Biden, the former vice president’s son, according to two GOP officials.

In the meeting, also attended by Senators John Cornyn of Texas, Mike Lee of Utah, and Lindsey Graham of South Carolina, McConnell appeared receptive to Cruz’s pitch, said the officials, who spoke on the condition of anonymity to discuss a private meeting. The discussions were first reported by Politico.

McConnell was receptive to the idea since it could enable the GOP to frame its position as being both supportive of the president and open to witnesses, one of the officials said. Cruz then talked up the idea at a broader lunch of all GOP senators, the officials said, and received encouragement.

The push by Cruz — and McConnell’s willingness to embrace an aggressive posture just before the trial is set to begin in earnest — shows how Senate Republicans are working to balance the party’s moderate wing, which has worked in recent weeks to shape GOP discussions over the trial, with its vocal conservative faction.


Cruz has long said Trump should be able to get the kind of witnesses he wants in a trial, while Democrats have balked at the prospect of having the Bidens or other GOP-sought witnesses testify, arguing that doing so would allow Trump to divert attention away from his own alleged wrongdoing. Trump prevented people with firsthand knowledge of his relations with Ukrainian officials from testifying during the impeachment inquiry in the House.

‘‘People can express their own view if they’d like,’’ Romney said Tuesday. ‘‘I intend to be as impartial as the oath requires.’’

Despite their role as potential swing GOP votes in a narrowly divided Senate, the group of moderates has yet to defect in any significant fashion from party leaders, who in turn have been willing to accommodate the group’s requests as Republicans finalize a measure that will set the parameters of the trial.

In a nod to the moderates, there is expected to be a provision guaranteeing a vote on whether the Senate could consider subpoenaing witnesses, according to two GOP officials familiar with the matter, who spoke on the condition of anonymity because the resolution has not been made public. Collins had indicated last week that she wanted to ensure senators will get to vote on the ability to call witnesses.


McConnell said Tuesday that both parties would get a say on witnesses, telling reporters: ‘‘I can’t imagine that only the witnesses that our Democratic colleagues would want to call would be called.’’

For weeks, Democrats have pushed for four current and former administration officials to testify, including Bolton and acting White House chief of staff Mick Mulvaney. Bolton, who could shed more light on whether Trump withheld military aid and a White House visit from Ukraine to force its president to investigate his political rivals, said last week that he would be willing to testify before the Senate if subpoenaed.

Romney said this week that he presumes he will vote in favor of hearing from Bolton, although he added that his view could change depending on what he hears from the trial. He also said Tuesday that he doesn’t ‘‘plan to put a list together’’ of desired witnesses. Last week, Murkowski said she would be ‘‘curious’’ as to what Bolton would have to say, but she had not made a commitment on whether she wants to hear from the former White House official.

‘‘I won’t know until we get there,’’ Murkowski said this week. ‘‘I need to hear first from both sides. I’ll only be able to formulate my questions [while listening] to the questions and responses from members. We’ll all have the opportunity to weigh in. That’s what we’re trying to do is make sure that we all have a guaranteed opportunity [to weigh in].’’


Others, like Collins and Alexander, have declined to specify which witnesses, if any, they would like to hear from and probably will not until after the first phase of the trial is over.

‘‘We have a constitutional responsibility here. Just because the House was a circus doesn’t mean the Senate needs to be,’’ Alexander said Tuesday. ‘‘So we should hear the case, not dismiss it. We should hear the arguments, we should ask our questions, and then we should vote on whether we need additional evidence. And I think that’s a fair and impartial way to go about it.’’

Collins, who is up for reelection this year, is poised to join three other Republicans in voting for a resolution curbing Trump’s military authority in Iran.

In July 2017, both Collins and Murkowski defied their party on health care, dooming Republican efforts to fully undo the Affordable Care Act. They were joined by Senator John McCain, Republican of Arizona; together, the three sank a measure that would have killed key funding and protections provided by the law.