Rod Rosenstein, the next-in-line litigator to oversee investigations into Donald Trump's campaign ties with Russian officials, has already achieved a rare trifecta: unanimous approval from the three most recent presidents.

That bipartisan confidence may convince a Senate panel on Tuesday to advance his confirmation as the next deputy attorney general, particularly amid trepidation over the White House's relationship with the Russians.

Take comfort. There's zero political agenda. You cannot sway Rod. - Steve Silverman, Baltimore criminal lawyer, on Rod Rosenstein

George W. Bush tapped Rosenstein as the U.S. attorney for the District of Maryland in 2005. Barack Obama's administration trusted him enough to keep him on as the top federal prosecutor there for another eight years.

"He's a straight shooter when it comes to the discretionary aspects of his job," says Baltimore criminal lawyer Steve Silverman, who has known Rosenstein for at least a decade.

To those with misgivings about how a Trump appointee might cave to political pressures, Silverman has reassuring words about the Harvard Law grad's reputation.

"Take comfort. There's zero political agenda," he says. "You cannot sway Rod from intervening in a prosecution. All the cases within his office are going to rise and fall on the strengths and weaknesses of the facts and the application of the law."

Rosenstein keeps a low profile, yet perhaps never before has the selection of a second-in-command at the Department of Justice attracted this much scrutiny this early in a presidential administration. Understandably so, given the tempestuous start to Trump's presidency and the cascade of Russia-related scandals to befall his administration. The latest controversy surrounds Rosenstein's probable boss, Attorney General Jeff Sessions.

U.S. Attorney General Jeff Sessions had two conversations with the Russian ambassador to the U.S. during the presidential campaign. He has recused himself from a probe into the Trump campaign's alleged correspondence with Russian officials. (Alex Brandon/Associated Press)

Sessions confirmed last week that he met twice with the Russian ambassador — encounters he did not disclose during his Senate confirmation hearings when asked specifically about contact with the Russians. Sessions said he would recuse himself from investigations into alleged ties between Trump's team and the Russians during the 2016 election campaign.

That means Justice Department oversight of the Trump-Russia probe would fall to his deputy.

Unsubstantiated wiretapping claims

As the longest-serving U.S. attorney in the country, Rosenstein, 52, should be up to the task, according to legal colleagues in Maryland. Asked to describe his reputation as a litigator, the same words come up repeatedly: Cautious. Thoughtful. No-nonsense. And, perhaps of most interest to some Democrats, apolitical.

In his role at the DOJ, Rosenstein would take over investigations that carry any whiff of Russian meddling in presidential campaign activities — for example, if Congress approves a probe into unsubstantiated claims tweeted Saturday by Trump alleging Obama wiretapped Trump Tower during the election.

Rosenstein is widely seen as a much-needed force of stability in the current administration.

"I can't think of a better person to jump into the turbulent waters down there," says Andy White, a former assistant U.S. attorney who came to know Rosenstein in Baltimore in the early 1990s. "Because whatever he decides to do, he's not going to be afraid of any political ramifications."

Sergey Kislyak, Russia's ambassador to the U.S., has emerged as the central figure in the investigations into the Trump team's connections with Russia. (Cliff Owen/Associated Press)

Democratic critics of the Trump administration are demanding that a special prosecutor or commission be named to take the Trump-Russia probe out of the hands of the DOJ. White has faith Rosenstein is independent-minded enough to come to that conclusion on his own, noting that Obama himself entrusted the Republican lawyer to co-lead the sensitive investigations into leaks of classified material from the National Security Agency.

"If he thinks independent counsel should be named, he'll name one. If not, he won't," White says. "But he'll explain why, and he's not going to be pushed around by either side."

He's not going to be pushed around by either side. - Andy White, former assistant U.S. attorney

Rosenstein is not expected to necessarily fall in line with a Trump administration that has committed to stand up against a "dangerous anti-police atmosphere."

Last week, Rosenstein announced an indictment against seven Baltimore police officers named in a racketeering scheme. Slate's Leon Neyfakh suggested this would amount to at least one key departmental boss "in the house of Sessions" who might be more "willing to investigate police misconduct" than Sessions himself. (The top law enforcement official in the land last week dismissed scathing DOJ reports flagging police abuses in Chicago, evidently without reading the reports beyond their summaries, according to the Washington Post.)

'Quintessential G-man'

Though he may lean conservative politically, Rosenstein should pass as a worthy nominee by any partisan stripe, says Jim Trusty, who served as chief of the organized crime and gangs section at the DOJ during the Obama years.

Trusty praised Rosenstein's appointment as "the first good sign that I can divine that the new administration is going to go with professional, aggressive, good prosecutors — not just political patronage."

Beyond intellect, Trusty says Rosenstein is a powerful presence in court, as he learned when they tried a case together around 2000.

Rosenstein, who faces his confirmation hearing Tuesday for the role of deputy attorney general, was appointed top federal prosecutor in Maryland by President George W. Bush and remained in the political post for the entire Obama administration. (Brian Witte/Associated Press)

"Holy crap, this guy can try a case," Trusty recalls. "Perfect diction, perfect way to let the jury understand a complex scenario, never needed a stitch of notes. It just flowed perfectly off his tongue. I watched 12 jurors fall in trust with him."

D.C. lawyer Megan Brown, who interned under Rosenstein in 2001, describes him as "the quintessential G-man" who serves his country on a code of "rock-solid ethics."

Though Rosenstein will be entering into high-profile and politically treacherous territory, she expects her mentor to remain unflappable amid a rocky beginning for Trump's young administration.

"The department is in exceedingly good hands at a particularly tough time," she says.

If confirmed, Rosenstein would replace Dana Boente, currently the acting deputy attorney general. In January, Boente replaced acting attorney general Sally Yates, an Obama holdover who was sacked by Trump after she instructed the DOJ not to enforce Trump's first immigration travel order.