Former New York City Mayor Rudy Giuliani had a bold prediction about the Russia investigation when he joined President Trump’s legal team this week: “I don’t think it’s going to take more than a week or two,” he told the New York Post, “to get a resolution.”

That might seem like a far-fetched statement about an investigation that’s already lasted a year and has resulted so far in more than 100 charges against 19 people and three companies.

“My reaction to his statement? ‘Ha-ha,'” Peter Zeidenberg, who was deputy special counsel in the Scooter Libby case and worked with Mueller at the Justice Department, said over email. “The time-table is controlled by Mueller, not Trump or Giuliani.”

But allies in Trump’s legal world say they hope that Giuliani can leverage his expertise and personal relationships to bring an end to the probe hanging over the president.

“I have no idea how realistic it is,” says Victoria Toensing, a lawyer who nearly joined Trump’s legal team last month before conflicts prevented her from doing so. “If anyone can do that, it would be Rudy.”

Trump also mentioned in a statement about Giuliani’s hire, saying he “wants to get this matter quickly resolved for the good of the country.”

The special counsel’s office declined to comment.

Giuliani joins a team that has seen dramatic turnover in recent weeks — former lead lawyer John Dowd quit the team in March — and has reportedly been struggling to fill open positions. Dowd now expresses support for Giuliani’s hire: “I’m for Rudy,” he says. In the meantime Jay Sekulow, known for taking on religious freedom cases, has been in the lead on the outside team for Russia matters.

“Jay Sekulow was drinking from a fire hose,” says Toensing. “I don’t care how great you are — and I think the world of Jay — you can’t fight somebody with two hands tied behind your back. You’ve got to have the personnel power.”

Sekulow announced the hire of two other lawyers this week: the husband-and-wife team of Jane Serene Raskin and Marty Raskin. About Giuliani, Sekulow said in a statement, “We welcome his expertise.”

Former New York City mayor and federal prosecutor, Giuliani earned the praise of numerous lawyers in Trump’s orbit, many of whom say his particular experiences will be useful in his new role.

“He knows all that New York stuff,” says Toensing. “He knows New York, he knows the Justice Department, and he knows Trump.”

Giuliani’s old U.S. Attorney’s Office, the Southern District of New York, is currently investigating Trump’s longtime personal lawyer Michael Cohen, on a referral from Mueller’s office. FBI agents raided Cohen’s office in April and seized documents, including those related to Cohen’s payment to porn star Stormy Daniels.

Giuliani earned his spot in Trump’s circle during the campaign, when he was a frequent and fiery surrogate for the candidate on television and at rallies.

“I am sick and tired of the defamation of Donald Trump by the media and by the Clinton campaign. I am sick and tired,” he said during an energetic speech at the Republican National Convention in July 2016. “This is a good man.” Trump reportedly considered Giuliani for Secretary of State before Giuliani withdrew from contention in December 2016.

While Giuliani’s bombast and ego likely attracted the admiration of the president, others are more critical, including former FBI Director James Comey, who recounts working for Giuliani in the U.S. attorney’s office in the 1980s in his new book A Higher Loyalty.

“It took me a while to realize that Giuliani’s confidence was not leavened with a whole lot of humility. The cost of that imbalance was that there was very little oxygen left for others,” Comey wrote. “Though Giuliani’s confidence was exciting, it fed an imperial style that severely narrowed the circle of people with whom he interacted, something I didn’t realize was dangerous until much later: a leader needs the truth, but an emperor does not consistently hear it from his underlings.”

Giuliani is now stepping into a complex legal situation where some questions remain unresolved. The White House has been publicly wishing for the investigation to end for months, and Mueller’s team and Trump’s are still negotiating over whether the president will sit for an interview, among other matters.

Richard Ben-Veniste, who was one of the lead prosecutors on the Watergate Special Prosecution Force and knows Giuliani from the U.S. Attorney’s Office, says it’s “highly unlikely” that Giuliani can push the investigation to a rapid close. If Trump does sit for an interview, for example, that will take some time to prepare for. “The job of preparation for an interview of this importance requires a skilled lawyer and diligence of preparation on the part of the client,” he says. “I think there’s much more to do in the investigation.”

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Write to Tessa Berenson at tessa.berenson@time.com.