FBI Director James Comey is being thrust into the spotlight as the controversy surrounding Hillary Clinton Hillary Diane Rodham ClintonJoe Biden looks to expand election battleground into Trump country Biden leads Trump by 12 points among Catholic voters: poll The Hill's Campaign Report: Biden goes on offense MORE’s personal email server intensifies.

The FBI is investigating the security of the former secretary of State's email setup, including if classified information was mishandled. The probe is putting the nation’s top law enforcement agency at the center of a political battle leading into the 2016 election.

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Comey has long shown an independent streak that's gained him wide bipartisan praise and helped him sail to a 93-1 confirmation vote in the Senate. That independence will be tested with Republican lawmakers demanding answers and Clinton's presidential campaign team being dismissive of a controversy it sees as politically drummed up.

Comey has been in the middle of bruising fights before.

He's best known in Washington for a dramatic late-night standoff a decade ago with then-White House counsel Alberto Gonzáles over reauthorizing a domestic surveillance program.

Comey was acting attorney general in March 2004 when then-Attorney General John Ashcroft was hospitalized in intensive care. He raced to the hospital bed at The George Washington University Hospital after learning that Gonzáles was trying to get a semi-conscious Ashcroft to sign off on reauthorizing the National Security Agency's programs, arriving only moments before the White House lawyer.

A nearly incapacitated Ashcroft refused to sign the papers, saying "I'm not the attorney general. There is the attorney general,’" and pointing to Comey, who recounted the incident before the Senate in 2007.

Comey said he was “concerned that this was an effort to do an end-run around the acting attorney general and to get a very sick man to approve something” the Department of Justice had raised legal concerns about.

Ultimately, the Bush administration reauthorized the program without the Justice Department signing off, something that nearly drove Comey to step down, with his unsent resignation letter later published in The Washington Post.

It wasn't the first time Comey took a high-profile stand. As a U.S. attorney, he prosecuted businesswoman Martha Stewart for obstruction of justice in a probe into stock sales.

"I had to ... because if it was Jane Doe she would have been prosecuted," Comey said, looking back on the case in 2009. "I thought of my hesitation about the case due to someone being rich and famous, and how it shouldn't be that way."

And in the Bush administration, he appointed a special counsel in 2003 to investigate the CIA leak case that ultimately led to Scooter Libby, then-Vice President Dick Cheney’s chief of staff, being found guilty of perjury.

As FBI director, Comey has gone after other big names, including then-CIA Director David Petraeus for mishandling classified information. Petraeus resigned and later pleaded guilty, a stunning fall for an official who once garnered presidential buzz. And Sen. Bob Menendez Robert (Bob) MenendezKasie Hunt to host lead-in show for MSNBC's 'Morning Joe' Senators ask for removal of tariffs on EU food, wine, spirits: report VOA visa decision could hobble Venezuela coverage MORE (D-N.J.) is now facing federal corruption charges, the first sitting senator indicted since 2008.

Comey’s also seen his share of controversy as FBI chief, including a speech where he said all law enforcement officials are “a little bit racist.” And the U.S. ambassador to Poland apologized to that country after Comey suggested many Poles aided in the Holocaust, calling them “murderers and accomplices” who believed they “didn’t do something evil.”

Comey is now under pressure from both Republican lawmakers and the Clinton campaign as the FBI investigates the Democratic front-runner's emails.

Clinton has handed over her private email server and a backup drive to the FBI. The agency has been tight-lipped about its probe and signaled it intends to move at its own deliberate pace, even in the face of an impatient Congress.

Sen. Ron Johnson Ronald (Ron) Harold JohnsonThis week: Supreme Court fight over Ginsburg's seat upends Congress's agenda GOP set to release controversial Biden report Democrats fear Russia interference could spoil bid to retake Senate MORE (R-Wis.), the chairman of the Senate Homeland Security and Governmental Affairs Committee, called Clinton’s move a “first step” but vowed to keep a close eye on the probe.

“Questions remain unanswered about how Secretary Clinton and her team secured and preserved sensitive government information in their possession,” he said. “As chairman of the Homeland Security and Governmental Affairs Committee, I have an obligation to continue asking these questions to ensure the proper preservation and security of Secretary Clinton’s records.”

So far, Republican lawmakers have expressed confidence in Comey, but made clear they have high expectations.

Judiciary Committee Chairman Chuck Grassley Charles (Chuck) Ernest GrassleyGardner signals support for taking up Supreme Court nominee this year Grassley, Ernst pledge to 'evaluate' Trump's Supreme Court nominee McConnell digs in on vow to fill Ginsburg's Supreme Court seat MORE (R-Iowa) said Comey “has a reputation for applying the law fairly and equally regardless of politics,” adding that he’s counting on him to get to the bottom of the controversy.

“It is critical that he upholds that standard in this matter and that he keeps Congress informed so that the public can have confidence in the integrity of the FBI’s inquiry,” he said. “[The] director should ensure that the FBI finds out who is responsible for any mishandling of classified information, wherever the facts lead.”

Grassley is already pressing Comey for more information on Huma Abedin, a top Clinton aide.

Rep. Trey Gowdy Harold (Trey) Watson GowdySunday shows preview: Election integrity dominates as Nov. 3 nears Tim Scott invokes Breonna Taylor, George Floyd in Trump convention speech Sunday shows preview: Republicans gear up for national convention, USPS debate continues in Washington MORE (R-S.C.), who chairs the House Benghazi panel, said he wouldn’t armchair quarterback Comey’s investigation, citing his “reputation for even-handedness and fairness.”

“I'm going to have to count on the bureau and Jim Comey,” he told Fox News’s “America’s Newsroom.”

“The same folks who investigated and prosecuted General Petraeus are looking into the current allegations with respect to classified information and if the facts are the same then I expect the result to be the same."

Democrats are watching closely as fears grow that a prolonged probe could damage Clinton’s campaign. Polls already show Clinton is vulnerable on issues of transparency and trust with voters.

The campaign has denied any wrongdoing and dismissed claims that Clinton received classified material on a private server as “misinformation” and “nonsense.”

The FBI, for its part, declined to comment on the investigation, including potential next steps or Comey's role.

A spokesman for the FBI said the agency isn’t answering questions about Clinton’s email server.

“We do not anticipate this will change,” the official said.

Despite the agency’s attempt to put space between itself and the brewing political storm, Comey faces tough decisions that could affect the future of the Clinton campaign.

During his confirmation hearing in 2013, Comey acknowledged the challenges of the job, saying that the FBI “cannot be associated with any interest or any party or any group."

“FBI must be about finding the facts and only the facts,” he said.