"We take the position that we want to hear from witnesses," Brown said. "I don't know what Hunter Biden has to do with the phone call the president made."
Sen. Sherrod Brown, D-Ohio, said Sunday that he's "fine" with Republicans calling former Vice President Joe Biden's son Hunter Biden as a witness in President Donald Trump's upcoming impeachment trial.
"We take the position that we want to hear from witnesses," Brown told CNN's "State of the Union." "I don't know what Hunter Biden has to do with the phone call the president made."
"I think many Republicans think that's a distraction," he added. "That's what Republican senators tell me quietly."
Democrats and Republicans have been battling for weeks over just how much more information will be presented at the trial, which is set to begin Tuesday.
Brown said it would be unjustifiable to not call additional witnesses nor introduce any new information that is related to the trial. He echoed Senate Minority Leader Chuck Schumer, D-N.Y., in calling for witness testimony from "people who were in the room" and were "eyewitnesses" to the president's efforts regarding Ukraine.
Schumer has said he wants to hear from four current and former Trump administration officials, including acting White House chief of staff Mick Mulvaney and former national security adviser John Bolton. Bolton has said he would testify if subpoenaed by the Senate. Trump has suggested he would block Bolton's testimony.
Senate Majority Leader Mitch McConnell, R-Ky., has said the question of additional witnesses and documents will be determined by a vote after initial arguments are presented by both sides. The House passed two articles of impeachment against the president: one for abusing his power by pressuring Ukraine to investigate former Vice President Joe Biden and his son Hunter and the other for obstruction of Congress.
McConnell has suggested that the former vice president's son could be called as a witness in impeachment — something Trump and his allies have suggested they want to have happen.
Speaking with Fox News' "Sunday Morning Futures," Sen. Ted Cruz, R-Texas, called Hunter Biden "such an important witness," though he did not commit to voting in favor of calling witnesses in the trial. Sen. Lindsey Graham, R-S.C., told "Fox News Sunday" that Republicans "can look at" the Bidens "outside of impeachment."
Sen. Dick Durbin, D-Ill., told NBC's "Meet the Press" that the issue of whether to call the younger Biden in the trial is in dispute among Republicans.
"We've been told even within their caucus there's dispute as to whether that's really in their best interest," he said.
Trump and allies, lead by his personal attorney Rudy Giuliani, have for months argued that the younger Biden's time on the board of the Ukrainian gas company Burisma, while his father oversaw Ukraine policy in the Obama administration, was corrupt. Most notably, they have advanced the unsubstantiated claim that the then-vice president, now a leading 2020 contender, took steps to protect his son from an investigation into that company.
But earlier this year, Bloomberg News, citing documents and a former Ukrainian official, reported the Burisma investigation was dormant for more than a year before Biden called for then-top Ukrainian prosecutor Viktor Shokin to step down. Politifact, meanwhile, reported it found no evidence to "support the idea that Joe Biden advocated with his son's interests in mind."
Biden's 2016 call for Shokin's ouster was widely backed by the international community, as Shokin was seen as ineffective and refusing to probe corruption. He was later removed by the country's parliament.
It was during the president's July 25 call with Zelenskiy that Trump asked his counterpart to probe the Bidens. That call set off a series of events that led to Trump's impeachment.
Speaking with ABC's "This Week," Sen. Cory Booker, D-N.J., said "these assaults on the Biden family are not relevant to what's at issue in this case."
"And this is an invitation to try to muddle waters," he said.
House Judiciary Committee Chairman Jerry Nadler, D-N.Y., told CBS's "Face the Nation" that the younger Biden "has no knowledge of the accusations against the president."
"Did the president, as we said — as the evidence shows that he did— betray his country by conspiring with a foreign country to try to rig the election?" Nadler, a House impeachment manager, said. "Hunter Biden has nothing to say about that. They're asking for Hunter Biden is just more of a smear of Hunter Biden that the president's trying to get the Ukraine to do."
The battle over witnesses and documents increased this week after the House released a trove of documents from indicted Giuliani associate Lev Parnas, who spoke extensively with MSNBC and CNN about his efforts to dig up dirt in Ukraine. Then on Thursday, the nonpartisan Government Accountability Office said in a decision that the Trump administration broke the law by withholding nearly $400 million in aid to Ukraine.
Republicans pushed back on the idea of Parnas testifying. Sen. David Perdue, R-Ga., told "Meet the Press" that Parnas' information was "second hand" and "a distraction," though Parnas had worked closely with Giuliani in Ukraine.
Sen. John Cornyn, R-Texas, told "Face the Nation" he "would be careful before crediting the veracity of somebody who is under indictment in New York, the southern district of New York, and who's trying to get leniency from the prosecutor and who has ties to Russian oligarchs."
Cornyn added "there's no question that there have been a series of grifters and other hangers-on that have associated themselves with the president's campaign or claimed to have special relationships with the president."
Asked if he had any questions for Giuliani about Parnas, Cornyn said the former mayor is "not relative to the impeachment."
"That's a relationship that causes many of us to sort of scratch our heads," he said. "But I'd say he's not relevant to the articles and what the Senate's gonna be asked to do, impeaching a president for the third time in American history for a non-crime over events that never occurred."