WASHINGTON — Senator Rand Paul clashed publicly on Thursday with Chief Justice John G. Roberts Jr. after the Kentucky Republican tried and failed to ask a question at President Trump’s impeachment trial that would have named the person widely thought to be the whistle-blower whose complaint formed the basis for the charges.
In a striking moment on the Senate floor, Chief Justice Roberts, who is presiding over the trial and has the task of reading senators’ questions aloud, refused to read one from Mr. Paul, instead saying: “The presiding officer declines to read the question as submitted.”
Mr. Paul, visibly angry at being thwarted by the chief justice, quickly left the Senate chamber while the trial was still in session and rushed to a news studio upstairs in the Capitol, where he read the question the chief justice had rejected — and the name of the individual in question — in front of television cameras, complaining that his question “deserved to be asked.”
“I think it was an incorrect finding not to allow the question,” he told reporters.
The extraordinary back and forth reflected the determination of some of Mr. Trump’s staunchest defenders on Capitol Hill to shift the focus of the impeachment proceeding away from the president’s conduct and toward what many Republicans suggest was a plot by his opponents to manufacture a basis for removing him.
Mr. Paul’s question asked whether the House impeachment managers or members of the president’s legal defense team were aware of reports that two individuals “may have worked together to plot impeaching the president before there were formal House impeachment proceedings.” Moments after meeting with reporters, Mr. Paul also posted the question, including the person’s name, on Twitter.
His push to ask the question began on Wednesday, when he submitted it and it was repeatedly rejected, according to people familiar with the matter who spoke on condition of anonymity to discuss it. On Thursday, Mr. Paul escalated the matter, standing up in the Senate chamber and handing forward a handwritten card bearing the question, in line with the trial rules. Chief Justice Roberts paused to read it silently, then turned instead to a piece of paper he had on the desk in front of him and appeared to read a prepared line indicating his decision not to ask the question aloud.
The Kentucky Republican’s disclosure of the person’s name was not the first time that he has done so. He has repeatedly urged media organizations to reveal the person’s name, and in at least one interview with a Washington radio station, he said it aloud himself.
There are federal whistle-blower protections in place designed to prevent workplace retaliation and to make it more difficult to fire, demote or harass civil servants who report wrongdoing. Although neither the Intelligence Community Whistleblower Protection Act of 1998 nor related statutes explicitly give a whistle-blower the right to anonymity, some lawyers and experts have said exposing the identity of a whistle-blower could expose them to retribution or be tantamount to trying to intimidate a witness.
Joseph Maguire, the acting director of national intelligence, has said the whistle-blower followed the procedures properly, and intelligence officials have informally told their staffs that the anonymity of the whistle-blower should be respected.
Like Mr. Paul, conservative news organizations and activists have sought to focus attention on the whistle-blower’s identity since October, just weeks after the intelligence officer first expressed concerns about Mr. Trump’s July 25 call with the president of Ukraine. The call prompted the House inquiry that eventually led to Mr. Trump’s impeachment and the Senate trial.
As the impeachment inquiry expanded beyond the allegations contained in the whistle-blower’s initial complaint, Mr. Trump’s defenders repeatedly pressed for examination of the whistle-blower’s motives. They argued that the effort to remove Mr. Trump from office was a deep-state conspiracy orchestrated by unelected bureaucrats loyal to former President Barack Obama and working in concert with Representative Adam B. Schiff of California, the Democratic chairman of the House Intelligence Committee.
They seized on a report by The New York Times that Mr. Schiff learned through an aide about the outlines of a C.I.A. officer’s concerns about Mr. Trump’s dealings with Ukraine a few days before the officer filed a whistle-blower complaint.
At the news conference, Mr. Paul asserted that the two had been “working together for years looking for an opportunity” to impeach the president.
Several House Republicans loyal to Mr. Trump asked questions about the person widely believed to be the whistle-blower during the closed-door depositions of witnesses conducted by the Intelligence Committee. The interviews were later transcribed and released publicly. Representative Louie Gohmert, Republican of Texas, used the person’s name during an open committee hearing in December.
Democrats argue that the focus by Mr. Paul and other conservatives on the whistle-blower is misplaced, because the House investigation uncovered extensive evidence corroborating and expanding upon the initial allegations. Mr. Schiff and others have also criticized the push to reveal the person’s name, saying it puts the person in danger and makes it less likely that other whistle-blowers will come forward in the future.
In his news conference on Thursday, Mr. Paul insisted that his question had nothing to do with unmasking a whistle-blower, saying he was merely trying to get information about people who might have been working inside the government against Mr. Trump’s interests. He said the question “made no reference to any whistle-blower or any kind of person, a complaint from the whistle-blower.”
In a statement after the news conference, Sergio Gor, a spokesman for Mr. Paul, said in a statement that the senator “wanted to ask about various individuals who worked for President Obama’s administration and whether they colluded with Adam Schiff. Nowhere does he allege, nor does he know if, any of them are the so-called ‘whistle-blower.’ Those reporting otherwise are misreporting.”
But Mr. Paul’s efforts to reveal the name have put him at odds with many of his colleagues, including Republicans.
Just before Mr. Paul sent his question to the desk on Thursday, Senator Mitch McConnell of Kentucky, the majority leader, made comments as he opened the day’s question period that appeared to be directed at discouraging Mr. Paul’s actions.
“We’ve been respectful of the Chief Justice’s unique position in reading our questions,” Mr. McConnell said. “And I want to be able to continue to assure him that that level of consideration for him will continue.”
Hours before Mr. Paul tried to reveal the person’s name on the Senate floor, Senator Lindsey Graham, Republican of South Carolina, said that he did not believe that should happen.
“Not in this environment,” he told reporters.
Nicholas Fandos contributed reporting.