Facing Republican lawmakers' allegations of impropriety in the investigation into Russian interference in the 2016 elections, Deputy Attorney General Rod Rosenstein defended the man leading the investigation in a hearing Wednesday.

Republican congressmen repeatedly questioned the integrity of Robert Mueller, the special counsel, alleging his investigation is tainted because prosecutors and agents on his team are biased against President Donald Trump. Attorney General Jeff Sessions recused from the investigation, effectively placing Rosenstein in charge of Mueller. Asked by Rep. Steve Cohen, D-Tennessee, if Rosenstein saw any reason to fire Mueller, he said he's seen no “good cause” to do so.

Cohen asked Rosenstein what he would do if ordered to fire the special counsel, as some Democrats fear Trump may do. Rosenstein said he would only fire Mueller for cause, consistent with the regulations that govern special counsels.

“I would follow the regulation,” Rosenstein said. “If there were good cause, I would act. If there were no good cause, I would not.”

Cohen also asked if Trump ever indicated to Rosenstein that he may want Mueller removed. The deputy attorney general declined to discuss any conversations he may have had with the president, but said no one had communicated to him a desire to remove Mueller.

Asked why Rosenstein appointed Mueller in the first place, the deputy attorney general praised the special counsel.

“I believe that based upon his reputation, his service, his patriotism, and his experience with the department and with the FBI, I believe he was an ideal choice for this task,” Rosenstein said.

Rosenstein also defended Mueller's oversight of potential bias within his investigation.

Media reports Tuesday night showed two FBI agents assigned to Mueller's investigation exchanged several text messages criticizing Trump, including one that called the president an “idiot.” One of the agents was removed from Mueller's team in July after the special counsel found out about the texts, and another had already ended her detail with the team, according to reports.

There have also been questions about bias on Mueller's team because many members have donated to Democratic campaigns. But Rosenstein said he did not see any indication of impropriety.

Rosenstein said the text messages were unearthed as part of an inspector general's investigation into conduct at the FBI, and that he would not discuss the IG's investigation. But he added he did not think there was any impropriety on Mueller's team, and that bias and political affiliation are different.

“I've discussed this with Director Mueller, and he and I collectively have a lot of experience managing offices in the Department of Justice,” Rosenstein said. “We recognize we have employees with political opinions and it's our responsibility to make sure those opinions do not influence their actions. So I believe Director Mueller understands that and that he is running that office appropriately.”

Rosenstein also faced questions about the scope of Mueller's investigation, which he largely refused to answer, referring senators back to his initial order that created the special counsel investigation.

Trump has previously said Mueller would be exceeding his authority if he looked into the president's personal finances. Asked by Rep. Lamar Smith, R-Texas, whether Mueller has ever requested to expand the scope of his investigation, Rosenstein declined to give specifics.

He confirmed that Mueller would need to seek Rosenstein's permission to expand his probe, but said Mueller can choose to include matters in his investigation that may seem ambiguous as to whether they fall under the scope.

“There are a lot of media stories speculating about what the special counsel may or may not be doing,” Rosenstein said. “I know what he's doing. … I can assure you that the special counsel is conducting himself consistently with our understanding about the scope of his investigation.”

Facing Republican lawmakers' allegations of impropriety in the investigation into Russian interference in the 2016 elections, Deputy Attorney General Rod Rosenstein defended the man leading the investigation in a hearing Wednesday.

Republican congressmen repeatedly questioned the integrity of Robert Mueller, the special counsel, alleging his investigation is tainted because prosecutors and agents on his team are biased against President Donald Trump. Attorney General Jeff Sessions recused from the investigation, effectively placing Rosenstein in charge of Mueller. Asked by Rep. Steve Cohen, D-Tennessee, if Rosenstein saw any reason to fire Mueller, he said he's seen no “good cause” to do so.

Cohen asked Rosenstein what he would do if ordered to fire the special counsel, as some Democrats fear Trump may do. Rosenstein said he would only fire Mueller for cause, consistent with the regulations that govern special counsels.

“I would follow the regulation,” Rosenstein said. “If there were good cause, I would act. If there were no good cause, I would not.”

Cohen also asked if Trump ever indicated to Rosenstein that he may want Mueller removed. The deputy attorney general declined to discuss any conversations he may have had with the president, but said no one had communicated to him a desire to remove Mueller.

Asked why Rosenstein appointed Mueller in the first place, the deputy attorney general praised the special counsel.

“I believe that based upon his reputation, his service, his patriotism, and his experience with the department and with the FBI, I believe he was an ideal choice for this task,” Rosenstein said.

Rosenstein also defended Mueller's oversight of potential bias within his investigation.

Media reports Tuesday night showed two FBI agents assigned to Mueller's investigation exchanged several text messages criticizing Trump, including one that called the president an “idiot.” One of the agents was removed from Mueller's team in July after the special counsel found out about the texts, and another had already ended her detail with the team, according to reports.

There have also been questions about bias on Mueller's team because many members have donated to Democratic campaigns. But Rosenstein said he did not see any indication of impropriety.

Rosenstein said the text messages were unearthed as part of an inspector general's investigation into conduct at the FBI, and that he would not discuss the IG's investigation. But he added he did not think there was any impropriety on Mueller's team, and that bias and political affiliation are different.

“I've discussed this with Director Mueller, and he and I collectively have a lot of experience managing offices in the Department of Justice,” Rosenstein said. “We recognize we have employees with political opinions and it's our responsibility to make sure those opinions do not influence their actions. So I believe Director Mueller understands that and that he is running that office appropriately.”

Rosenstein also faced questions about the scope of Mueller's investigation, which he largely refused to answer, referring senators back to his initial order that created the special counsel investigation.

Trump has previously said Mueller would be exceeding his authority if he looked into the president's personal finances. Asked by Rep. Lamar Smith, R-Texas, whether Mueller has ever requested to expand the scope of his investigation, Rosenstein declined to give specifics.

He confirmed that Mueller would need to seek Rosenstein's permission to expand his probe, but said Mueller can choose to include matters in his investigation that may seem ambiguous as to whether they fall under the scope.

“There are a lot of media stories speculating about what the special counsel may or may not be doing,” Rosenstein said. “I know what he's doing. … I can assure you that the special counsel is conducting himself consistently with our understanding about the scope of his investigation.”