Several Senate Democrats are privately discussing the possibility of calling Republicans’ bluff on witnesses, weighing an unusual trade in President Trump’s impeachment trial: the testimony of Hunter Biden for the testimony of a key administration official.

Publicly, most Democrats have scoffed at the growing GOP clamor to hear former vice president Joe Biden’s son testify, dismissing him as irrelevant to the charges against Trump and accusing Republicans of trying to distract from the allegations against the president.

But behind closed doors, a small group of Democratic senators and aides has begun to question that logic, sounding out colleagues on whether to back a witness deal that could lead to testimony from former national security adviser John Bolton or other administration officials with possible firsthand knowledge of the Ukraine controversy, according to multiple Democratic officials who spoke on the condition of anonymity to describe the private discussions.

These Democrats said they believe having Hunter — or possibly Joe Biden — testify could backfire on Trump and the GOP, giving Biden and the party a platform to strike back and paint Republicans and the White House as obsessed with trying to damage one of Trump’s 2020 presidential rivals.

“If you want to give Joe Biden an opportunity to sit in the well of the Senate and answer the question, ‘Do you think the president acted appropriately?’ go right ahead,” said Sen. Christopher A. Coons (D-Del.), a Biden supporter who is close with the family. Coons has not discussed the matter with Biden or Democratic leaders but said his longtime friend could hold his own.

“I can’t imagine a person more comfortable in the well of the Senate than a man who spent 36 years here as a United States senator,” he said.

Senate Minority Whip Richard J. Durbin (D-Ill.) said Hunter Biden is immaterial to the impeachment charges, but he left the door open to the possibility of having him testify.

“If there are four Republicans who open the conversation about witnesses, then I assume there will be a negotiation that follows — but I can’t tell you where it goes,” he said.

The discussions about the Bidens are being closely held, and the issue is fraught for Democrats, due to the differing levels of support for Biden in a chamber stocked with presidential candidates and the clashing views on impeachment strategy. In private conversations in recent days, there has been much loathing of the Republicans’ spotlight on the Bidens among Senate Democrats, but also a fear that unless a witness deal is eventually struck, the trial could proceed without witnesses, according to party officials and Senate aides.

That predicament has led to discussions about whether, down the line, Hunter Biden or Joe Biden should be considered as part of a witness proposal. But there is hesitancy to raise the issue publicly until Senate Democratic leaders signal interest, the officials and aides said.

“Whether I’d make a trade or not, I’d have to think about it, but the question is then: Well, how does that get us more information about the charges that have been put forth?” said Sen. Jon Tester (D-Mont.), who added that he believed Hunter Biden was irrelevant to Trump’s impeachment charges.

The House impeachment charges center on the allegation that Trump withheld military aid and a White House meeting to pressure Ukraine to investigate the Bidens, as well as a discredited theory that Ukraine worked with Democrats to interfere in the 2016 election.

Hunter Biden served on the board of a Ukrainian gas company, Burisma, when his father served as vice president. Trump and his personal lawyer Rudolph W. Giuliani have promoted an unfounded allegation that Biden tried to stop a corruption investigation in Ukraine to protect his son, who is no longer on Burisma’s board. Hunter Biden was not accused of wrongdoing.

Inside Biden’s 2020 operation, there is little interest in publicly engaging with what Biden’s advisers and friends dismiss as “a stupid Republican talking point,” said a person familiar with the campaign’s stance on the issue, who like others involved with the former vice president spoke on the condition of anonymity to discuss the issue. These people also described Biden as sensitive to how his family is covered in the media and used by political opponents.

“Biden and his people don’t want to give it credibility, so there is a stalemate right now, in terms of doing anything new,” one Biden associate said regarding whether the former vice president or his son would testify.

A Biden campaign aide sharply criticized Republicans on Tuesday for their emphasis on Hunter Biden amid Trump’s impeachment, calling it a “sad and obvious attempt at diversion.”

“Joe Biden was on the exact same page as Republicans and the rest of the Western world when he helped oust” Ukrainian prosecutor general Viktor Shokin in 2016, the Biden campaign aide said. “What’s more, Hunter Biden’s role with Burisma was announced in the spring of 2014 and was well-covered. The GOP didn’t say a word about any of this until now, half a decade later.”

The topic appears to also annoy some Senate Democrats who are wary of publicly discussing an issue they contend is political gamesmanship by Republicans and should not be a part of Trump’s trial. On Tuesday, Sen. Sherrod Brown (D-Ohio) scolded a reporter who inquired about the matter — even though he said Sunday on CNN’s “State of the Union” that he was “fine” with Hunter Biden testifying if it would lead to Trump officials appearing before the Senate.

“It’s a typical Donald Trump-Mitch McConnell distraction that the national media continues to play with and continues to assist them,” he said. “I rarely criticize the media, but I just, I continue to hear this ‘Hunter Biden’ stuff like this has anything to do with it. And it all helps [Senate Majority Leader] Mitch McConnell just to muddy the waters.”

Brown’s comments underscore how Democrats are grappling with whether to horse trade with Republicans on witnesses. If they make a deal and acquiesce to GOP demands on the Bidens, they’d be throwing one of their top 2020 candidates into the messy impeachment battle. But if they refuse to engage — and are unable to persuade enough Republicans to join them in demanding witnesses — they may never uncover what Trump said to his top aides about Ukraine.

For now, Senate Democrats are being advised by their leadership to reject the idea of a trade-off out of hand, keeping the focus instead on the GOP’s refusal to subpoena key administration officials who may have firsthand knowledge about Trump’s actions toward Ukraine.

“The whole discussion is silly because Hunter Biden is not a witness to this matter. . . . Why not call him as a witness in the O.J. trial?” said Sen. Angus King (I-Maine), who caucuses with Democrats.

Sen. Ted Cruz (R-Tex.) initially floated the idea of a Hunter Biden-for-Bolton trade-off during a private GOP meeting last week. Since then, Hunter Biden’s potential testimony has emerged as a potential flash point as it becomes clear that Republicans are determined to either avoid witnesses altogether or seek to trade one witness for another.

Most Democrats see the proposal by Cruz — which has been echoed by other supporters of the president — as an obvious gambit to prod Democrats toward a deal that would swing the spotlight away from Trump.

“Hunter Biden is not accused of withholding $391 million of congressional authorized defense spending for one of our allies who’s under attack by Russia,” said Sen. Thomas R. Carper (D-Del.), Biden’s home-state colleague in the Senate for many years. “Donald Trump is. We need to keep that in mind.”

Democrats interested in a possible deal said they would want an assurance from the president that he would not assert executive privilege over Bolton or whichever witness they choose. Most acknowledge that an agreement seems unlikely, even as they insist it isn’t off the table.

One Democrat argued it could be risky for the Biden campaign but said it could also give them a chance to steal the microphone from Trump. Additionally, some Democrats privately say Hunter, with his well-chronicled struggle with addiction, could come across as a sympathetic figure under GOP attacks.

One idea that has been informally floated, according to two people close to the Biden campaign, is to instead offer testimony from Joe Biden in exchange for testimony from Trump. That would allow Democrats to put the spotlight on Trump’s conduct while getting a chance to engage the president directly. Others have suggested that Biden could appear instead of his son, detailing his work fighting corruption in Ukraine and lambasting Republicans for attacking his family, which has been beset by tragedy.

Biden allies worry that allowing him or Hunter to get involved in impeachment would only distract from the former vice president’s effort to win the nomination. But Rep. Tim Ryan (D-Ohio), a Biden supporter, said the former vice president won’t let that happen, predicting that he “is going stay focused on the issues facing Youngstown, Ohio, and places like it.”

“Joe isn’t going to let the Republicans’ M.O. — trying to get Hunter to testify or whatever it is — distract him,” he said.

Paul Kane contributed to this report.