WASHINGTON — Attorney General William Barr on Wednesday will face lawmakers’ questions for the first time since releasing special counsel Robert Mueller’s Russia report, in what promises to be a dramatic showdown as he defends his actions before Democrats who accuse him of spinning the investigation’s findings in President Donald Trump’s favor.

Barr’s appearance before the Senate Judiciary Committee is expected to highlight the partisan schism around Mueller’s report and the Justice Department’s handling of it. It will give the attorney general his most extensive opportunity to explain the department’s actions, including a press conference held before the report’s release, and for him to repair a reputation bruised by allegations that he’s the president’s protector.

Barr is also invited to appear Thursday before the Democratic-led House Judiciary panel, but the Justice Department said he would not testify if the committee insisted on having its lawyers question the attorney general.

His appearance Wednesday will be before a Republican-led committee chaired by a close ally of the president, Sen. Lindsey Graham of South Carolina, who is expected to focus on concerns that the early days of the FBI’s Russia investigation were tainted by law enforcement bias against Trump.

Democrats are likely to focus on Barr’s statements and actions in the last six weeks that have unnerved them. The tense relations are notable given how Barr breezed through his confirmation process, picking up support from a few Democrats and offering reassuring words about the Justice Department’s independence and the importance of protecting the special counsel’s investigation.

The first hint of discontent surfaced last month when Barr issued a four-page statement that summarized what he said were the main conclusions of the Mueller report. In the letter, Barr revealed that he and Deputy Attorney General Rod Rosenstein had cleared Trump of obstruction of justice after Mueller and his team found evidence on both sides of the question but didn’t reach a conclusion.

Barr is likely to defend himself by noting how he released the report on his own even though he didn’t have to under the special counsel regulations, and that doing so fulfilled a pledge he made at his confirmation hearing to be as transparent as the law allowed. Barr may say that he wanted to move quickly to give the public a summary of Mueller’s main findings as the Justice Department spent weeks redacting more sensitive information from the report.

After the letter’s release, Barr raised eyebrows anew when he told a congressional committee that he believed the Trump campaign had been spied on, a common talking point of the president and his supporters. He also equivocated on a question of whether Mueller’s investigation was a witch hunt, saying someone who feels wrongly accused would reasonably view an investigation that way. That was a stark turnabout from his confirmation hearing, when he said he didn’t believe Mueller would ever be on a witch hunt.

A person familiar with Barr’s thinking has said that Barr, a former CIA employee, did not mean spying in a necessarily inappropriate way and was simply referring to intelligence collection activities. The FBI did obtain a secret surveillance warrant in 2016 to eavesdrop on the communications of Carter Page, a former Trump campaign aide.

Then came Barr’s April 18 press conference to announce the release of the Mueller report later that morning.

He repeated about a half dozen times that Mueller’s investigation had found no evidence of collusion between the campaign and Russia, though the special counsel took pains to note in his report that “collusion” was not a legal term and also pointed out the multiple contacts between the campaign and Russia.

In remarks that resembled some of Trump’s own claims, he praised the White House for giving Mueller’s team “unfettered access” to documents and witnesses and suggested the president had the right to be upset by the investigation, given his “sincere belief that the investigation was undermining his presidency, propelled by his political opponents, and fueled by illegal leaks.”

It remained unclear Tuesday whether Barr would appear before the House committee. That panel’s Democratic chairman, Rep, Jerrold Nadler of New York, said witnesses could too easily filibuster when questioned by lawmakers limited by five-minute time limits. Having lawyers do the questioning enables the committee “to dig down on an issue and pursue an issue.”

“And it’s not up to anybody from the executive branch to tell the legislative branch how to conduct our business,” Nadler said.

The committee will vote on allowing staff to question Barr at a separate meeting on Wednesday, at the same time Barr takes questions from the Senate.

The top Republican on the House Judiciary panel, Georgia Rep. Doug Collins, sharply criticized the plan. Nadler “has taken a voluntary hearing and turned it into a sideshow,” Collins said.

The Justice Department’s stance appears consistent with the Trump administration’s broader strategy of “undermining Congress as an institution,” said Elliot Williams, who previously served as deputy assistant attorney general in the department’s legislative affairs office in the Obama administration and as a lawyer on a Democratic-led Senate Judiciary Committee.

He said that if he were still advising an attorney general, he would resist the idea of staff questioning a Cabinet official. “It’s a rational response to not want them questioning the attorney general,” Williams said.