Key questions Mueller could face when he testifies this week

The reticent former special counsel is set to testify on Wednesday.

Lawmakers will get the chance to question one of Washington’s most elusive figures on Wednesday after House Democrats triumphed in requiring former special counsel Robert Mueller to testify in public before two congressional committees.

But after landing the notoriously reserved former FBI director -- whose only public comments since launching the probe lasted just nine minutes -- what do lawmakers hope to accomplish?

Specifically, did Mueller punt to Congress because Justice Department policy precludes prosecuting a president in office?

How he answers could prove key to making the case that impeachment is justified if Democrats choose to pursue that route. Republicans, on the other hand, hope to undermine Mueller's probe in defense of the president.

For his part, Mueller has signaled his intention to “not go beyond our report” in any remarks before Congress, fearing he could get dragged into a political slugfest. But last month, upon announcing Mueller's planned appearance, Rep. Adam Schiff, the Democratic chairman of the House Intelligence Committee, said that while Mueller remains “deeply reluctant” to testify, “Congress has questions that go beyond the report.”

“We have questions about the counterintelligence investigation and the role of the agents within his team, to questions about some of the prosecutorial decisions that were made. We have fact questions about some of the statements that were made in the report,” Schiff said. “So there are any number of issues that we wish to cover with him.”

Beyond trying to get him to clarify key passages in his 448-page report, Democrats hope that seeing and hearing the strait-laced Mueller on live television may draw the public’s attention back to the Russia investigation, which plagued the White House for more than two years.

“If [Mueller] says what was in the report -- and says it to the American people so they hear it -- that will be very, very important,” Rep. Jerry Nadler, D-N.Y., the chairman of the House Judiciary Committee, has said. “That will be important itself. Whether he goes farther than that, we'll see.”

Rep. Jackie Speier, a California Democrat on the House Intelligence Committee, put a finer point on Democrats’ intentions.

“You can't expect the American people to want to read 400 pages of that document,” Speier said. “They are more likely to listen to Bob Mueller, who has shown he has powerful gravitas.”

That powerful image Democrats hope to conjure could help hammer home the special counsel's findings, bring to life a report that most Americans haven't read and bolster public support for a possible impeachment inquiry.

More than 90 House Democrats – roughly one-third of their caucus -- now support pursuing impeachment proceedings, even as the public’s desire lags behind. According to an ABC News/Washington Post poll taken after the Mueller report was released, 56% of Americans opposed impeachment.

Democrats have thus far struggled to bring witnesses to Capitol Hill, having to rely on court battles for victories against a White House whose penchant to keep current and foreign administration officials from testifying has stalled Democrats’ probes. Jay Sekulow, the president’s personal attorney, said last month that “there are no legal moves that are being made” by the White House to block Mueller’s testimony.

Regardless of Democrats’ intentions, Mueller’s testimony could produce some compelling TV moments Wednesday between the taciturn former special counsel and committee members.

But staking so much on Mueller's appearance, Democrats risk falling flat – and Republicans hope to capitalize on the opportunity.

“It is going to backfire on the Democrats,” Rep. Mark Meadows, a top Republican on the House Oversight Committee, predicted after Mueller's testimony was announced. “Bob Mueller better be prepared, because I can tell you -- he will be cross-examined for the first time, and the American people will start see the flaws in his performance.”

Sen. Lindsey Graham, R-S.C., one of the president’s closest allies on Capitol Hill, predicted that Mueller’s testimony “will blow up in their face,” referring to Democrats, adding that “the conclusions can't change.”

One potential subject for Republicans’ questions could be Mueller's team of prosecutors – long a subject of President Trump’s ire and whom he frequently to as “angry Democrats.”

Meadows said inquiries about the political backgrounds of special counsel prosecutors remain “a legitimate question.”

On Monday, Trump lashed out at the former special counsel on Twitter.

"Highly conflicted Robert Mueller should not be given another bite at the apple," Trump wrote. "In the end it will be bad for him and the phony Democrats in Congress who have done nothing but waste time on this ridiculous Witch Hunt."

ABC News' Benjamin Siegel and Trish Turner contributed to this report.