Republicans on the Senate Judiciary Committee on Thursday will take the extraordinary step of putting one of the most politically treacherous and emotionally charged congressional hearings in recent memory in the hands of an unknown career prosecutor from Arizona with little comparable experience.

Rachel Mitchell, who was tapped to question Supreme Court nominee Brett M. Kavanaugh and Christine Blasey Ford about her allegations that Kavanaugh assaulted her in high school, has never been involved in such a high-profile case or faced the glare of the national media.

One aspect of her background that could be key: Mitchell, who runs the special victims division of the Maricopa County Attorney’s Office, championed a manual for local prosecutors that recommends questioning victims of sexual assault with a “neutral, fact finding attitude,” placing the “best interest of the victim” first.

Republicans hope her presence will help bring credibility to the hearing. Judiciary Committee Chairman Charles E. Grassley (R-Iowa) said she will help “depoliticize” the process.

But by choosing an unknown for the task, Republicans have taken a risk — gambling that Mitchell finds a way, in her first turn on the national stage, to successfully deliver tough but empathetic questions.

If Mitchell turns out to be the fair and evenhanded questioner that Republicans said they want, there could be dangers for the embattled nominee: What if Ford appears credible in the face of such questioning? What if Kavanaugh struggles?

“There’s no telling what’s going to happen here,” said Nick Ackerman, who served as an assistant special prosecutor during the Watergate scandal. “If she does what she normally does and she’s legitimate and is good at this because she’s been doing this for a long time, [Republicans] could find themselves in a major pickle.”

The hearing also carries risks for the committee’s 10 Democrats, a group that includes several aspiring presidential candidates. Any political showboating could contrast poorly with the calm delivery of a professional prosecutor, experts said.

“A thorough and temperate examination is called for,” said Richard Ben-Veniste, a former Watergate special prosecutor.

Mitchell is largely a mystery to many senators, several said Wednesday. The process of hiring her was guided largely by Grassley and his top committee aides.

At a private meeting with Republicans on the Judiciary Committee in Senate Majority Leader Mitch McConnell’s office on Monday evening, Grassley told the GOP senators that he had settled on a female prosecutor named Mitchell, according to two people briefed on the discussion.

“I think there was a consensus that something like that made sense, but in terms of selecting her, I’ve never met her,” said Senate Majority Whip John Cornyn (R-Tex.), who sits on the committee.

Colleagues who have faced her in court praised Mitchell as having an empathetic, professional questioning style.

“She was prepared. She was thorough. She definitely knew how to do the questions to elicit information that was needed,” said Erika Warner, a lawyer with the Maricopa County Office of the Legal Defender, which works with indigent defendants and who has watched Mitchell question witnesses in court. Warner said she had never seen Mitchell badger witnesses or treat them with disrespect.

Some Republicans privately acknowledged they wanted a woman to take the job of questioning Ford to avoid the optics of her being interrogated by the committee’s 11 white, male Republican members.

The hearing will be rigidly structured. Once it begins at 10 a.m., Grassley and the committee’s ranking Democrat, Sen. Dianne Feinstein (D-Calif.), will each have time to deliver an opening statement. Then Ford will give her opening remarks, followed by questions that will alternate between Republicans and Democrats in the order of seniority. Kavanaugh will testify after her.

Each senator will be given five minutes to ask questions of both Ford and Kavanaugh. But most — if not all — Republican senators are expected to delegate their time to Mitchell.

One major question, Ackerman said, is whether Mitchell will design her own line of inquiry or merely deliver questions provided to her by the Republicans.

Sen. Orrin G. Hatch (R-Utah), a committee member, said GOP senators will not dictate questions Mitchell must ask.

“We’re not telling her anything,” he said. “She’s highly skilled, and she’s looking at it objectively.”

A committee spokesman said Mitchell has been working closely with Grassley’s committee aides — including more than a dozen lawyers and law clerks who were hired temporarily to work on Kavanaugh’s confirmation — to develop possible lines of questioning. Staffers have also provided Mitchell their investigative work on the allegations.

A senior Republican aide said the committee hopes Mitchell will press Ford on the details she has said she cannot remember, including the timeline of events around her allegations about Kavanaugh. They also hope Mitchell will push Ford about when and how she decided to come forward and her interactions with Democratic staffers.

Senate Democrats said they had no plans to recalibrate their strategy in light of Mitchell’s role. Democratic senators on the Judiciary Committee have not closely compared notes about questions they plan to ask Thursday, according to two people familiar with internal discussions.

Sen. Christopher A. Coons (D-Del.), a member of the Judiciary Committee, predicted the outcome of Thursday’s hearing will “largely turn on what sort of tone and approach she takes.”

“If this is someone who has spent years as a prosecutor for sex crimes, that could mean one of two things,” Coons said. “Either this is someone who deeply understands, respects and fights for victims and is able to conduct questioning of Dr. Ford that is respectful, or this is someone who knows how to be aggressive and focused and take a prosecutorial tone, and I think that will not turn out well for the majority.”

Mitchell, 50, has spent her entire career with the county attorney’s office, which is responsible for prosecuting crime in the Phoenix area. She has won awards for victim advocacy and lectured on how to approach sex crimes.

Tracey Westerhausen, a registered Democrat and defense lawyer who said she has faced Mitchell in 30 cases, recalled a time when a hostile witness broke out in a coughing fit as Mitchell examined him.

Without missing a beat, Mitchell reached into her pocket, produced a lozenge and asked, ”May I offer you a cough drop?”

“It was touching, and it was funny,” Westerhausen said. “It shows the kind of person she is.”

Mitchell is a registered Republican and has donated to the campaign of Mark Brnovich, Arizona’s Republican attorney general.

Cindi Nannetti, the former head of the sex-crimes unit at the county attorney’s office — and Mitchell’s predecessor and former supervisor — said that she has never known Mitchell to be influenced by politics.

“Rachel will do her job as a professional,” she said. “And she will do it with the utmost respect to the committee. She does not play politics when it comes to anything involving her work.”

In 2005, Mitchell helped prosecute a former priest accused of abusing six boys in the late 1980s and early 1990s as the county reeled from a diocese-wide abuse scandal.

Joseph Reaves, a former Arizona Republic reporter who recently co-published a book about the sex abuse scandal in the Phoenix Diocese, said Mitchell was highly empathetic to victims and said he was stunned to learn that she had been chosen to question Kavanaugh and Ford this week.

“I remember her being so supportive of the sex abuse victims,” he said. “To find out that she was going to be the person to question a sex abuse victim on behalf of the GOP — I was taken aback.”

Nationally, Maricopa County is widely known as the home of Joe Arpaio, who served as sheriff from 1993 to 2017 and was convicted of criminal contempt before receiving a pardon from President Trump last year.

Mitchell works for the county’s elected prosecutor, in a department that is independent from the sheriff’s office.

When Arpaio’s office was found to have failed to thoroughly investigate hundreds of sex crimes that were reported between 2005 and 2007, Mitchell was one of the prosecutors assigned to sort through files and figure out which cases were still viable, Nannetti said. She later conducted training sessions for the sheriff’s office, in hopes of avoiding the same problems in the future.

Reaves predicted that neither Republicans nor Democrats would ultimately be pleased with Mitchell.

“She’s going to be so good,” he said, “that both sides are going to have problems with her.”

Alice Crites, Sean Sullivan, Tom Hamburger and Gabriel Pogrund contributed to this report.