At least four people with law enforcement experience are under consideration by President Trump to replace James Comey at the helm of the FBI, according to a White House official, including the congressman who led a two-year investigation of Hillary Clinton.

Rep. Trey Gowdy, a South Carolina Republican and former federal prosecutor who led the Benghazi investigation, and Alice Fisher, assistant attorney general for the Justice Department’s criminal division for President George W. Bush are under consideration. Mike Rogers, a former Republican congressman from Michigan who led the House Intelligence panel, and former New York City police Commissioner Ray Kelly also are on the list, said the official, who spoke on condition of anonymity.

That list is likely to grow, the official said.

Trump fired Comey on Tuesday after what White House spokeswoman Sarah Sanders described as months of rising frustration with the FBI director, dating back to Trump’s election. Comey was leading the FBI investigation into potential collusion between Trump campaign officials and Russian government agents who sought to manipulate the outcome of the U.S. presidential election. Comey also publicly dismissed Trump’s claim that former President Obama spied on him.

Trump disparaged Comey as “a showboat” and “a grandstander” in an interview with NBC News aired Thursday.

The firing has plunged the Trump White House into another political crisis, as Democrats have roundly castigated the decision, and some Republicans have expressed unease.

U.S. Rep. Trey Gowdy, R-S.C., questions U.S. Secret Service Director Julia Pierson during a House Oversight and Government Reform Committee hearing on Sept. 30, 2014.

Trump once called Gowdy’s Benghazi hearings a “disaster,” suggesting they fell short of producing enough damaging evidence against Clinton for her tenure as secretary of state during a 2012 attack in Libya that led to four American deaths. Gowdy supported Sen. Marco Rubio in the 2016 Republican primary elections before ultimately supporting Trump as the nominee.

Fisher, the former Bush administration lawyer, is a partner with Latham & Watkins in Washington and focuses on white-collar and international criminal cases, according to the firm’s website.

Rogers retired from Congress in 2015 after seven terms to pursue a career in talk radio. He advised the Trump presidential transition team on national security issues but was asked to leave at about the same time New Jersey Governor Chris Christie was removed as head of the transition.

Rogers, who declined to comment, had criticized Trump’s unsubstantiated claim in March that Obama spied on him, saying on CNN that the president had “put another quarter in the conspiracy parking meter.”

“It makes no sense to me whatsoever,” he said at the time. “The only winner in this whole thing is Vladimir Putin.”

But Rogers has also said that government officials who leak information to news media should be more aggressively pursued. That stance that may be attractive to Trump, who has frequently complained about leaks from his administration.

Two days after Comey’s firing, there is still shock within the Federal Bureau of Investigation, said a former senior agent with contacts within the bureau. Rank-and-file agents regard Trump’s decision on Comey’s replacement as a tipping point in the question over whether the FBI remains independent or becomes politicized under the new president, said the former agent.

Rogers is respected in foreign-policy and intelligence communities and he would likely be well received by Republican leaders in Congress, but Democrats would regard him as too political a choice. FBI agents also would prefer a director who is less political than Rogers, said the former agent, who asked not to be identified to protect his relationships within the bureau.

Rogers was chairman of the House Intelligence Committee when Obama fired former Defense Intelligence Agency director Michael Flynn in 2014. After Mike Pence replaced Christie as the head of the Trump transition effort toward the end of 2016, Flynn – by then one of Trump’s closest advisers – assumed control of national security issues. Rogers abruptly exited within days of that power shift.

Trump fired Flynn, his first national security adviser, in February for misleading Pence about the extent of his conversations with a Russian envoy before Trump’s inauguration.

Kelly, 75, is the first person from Trump’s native New York to rise from beat patrolman to police commissioner and was the longest-serving head of the nation’s largest police force, holding the post a total of 13 years.

Then-New York Police Commissioner Ray Kelly arrives for fashion designer Oscar de la Renta’s memorial service in Manhattan on Nov. 3, 2014.

He was appointed commissioner by Democratic Mayor David Dinkins and again by Republican Mayor Michael Bloomberg, who is also the founder and majority owner of Bloomberg LP. In between, he gained experience leading federal law enforcement agencies under President Bill Clinton as commissioner of the U.S. Customs Service and as undersecretary of enforcement at the U.S. Treasury Department. He is now vice chairman of K2 Intelligence.

Jim Pasco, a Trump ally and executive director of the Fraternal Order of Police, said Kelly would be an FBI director “right out of central casting.”

Other people floated as possible picks also include Dana Boente, a U.S. attorney who briefly filled in as acting attorney general after Trump fired Sally Yates in January; John Pistole, a former director of the Transportation Security Administration and a former FBI deputy director; and Michael Mason, a senior vice president at Verizon Inc. and a former FBI executive assistant director.

Sen. Mike Lee, a Utah Republican, asked White House officials on Wednesday to consider U.S. Appeals Court Judge Merrick Garland as a replacement for Comey, Lee spokesman Conn Carroll said. Obama nominated Garland for the U.S. Supreme Court last year, but Senate Republicans refused to consider him.

Judge Merrick Garland, President Obama’s choice to replace the late Justice Antonin Scalia on the Supreme Court meets with Sen. Gary Peters, D-Mich., on Capitol Hill on April 28, 2016.

Garland was previously a federal prosecutor who oversaw the 1995 Oklahoma City bombing investigation. Lee publicly suggested replacing Comey with Garland,, “instead of a special prosecutor” for the Russia investigation, in a Twitter post on Thursday.

Twenty Democratic state attorneys general, meanwhile, sent a letter to Deputy U.S. Attorney General Rod Rosenstein on Thursday calling on him to appoint a special counsel to investigate Russian allegations of interference in the election. Rosenstein, who has been in office for about two weeks, wrote a letter recommending Comey’s dismissal – at Trump’s request – that the White House has used as justification for the firing.

“As prosecutors committed to the rule of law, we urge you to consider the damage to our democratic system of any attempts by the administration to derail and delegitimize the investigation,” the attorneys general wrote. They included New York’s Eric Schneiderman, Maryland’s Brian Frosh and Maura Healey of Massachusetts.

Bloomberg’s Andrew Harris, Larry Liebert and Sahil Kapur contributed.