FBI Director James Comey. Alex Brandon/AP FBI Director James Comey is testifying before the Senate Judiciary Committee on Wednesday in a public hearing on FBI oversight, where he will likely face tough questions about his handling of the investigations into Hillary Clinton's use of a private email server and Russia's interference in the 2016 election.

The hearing is routine and is not expected to revolve around the bureau's probe into possible collusion between President Donald Trump's campaign and Russia.

Democrats, however, will likely ask Comey why he did not disclose that investigation sooner and chose instead to publicly revisit the Clinton email investigation 11 days before the election. Republicans, meanwhile, are expected to focus on leaks from the intelligence community to the press about the FBI's probe into Trump's Russia ties.

Republican Sen. Chuck Grassley, the chairman of the committee, will likely home in on the FBI's relationship with former British spy Christopher Steele, the author of an explosive but unverified dossier detailing the Trump campaign's ties to Russia. Grassley has sent two letters to Comey asking him to clarify reports that the bureau offered to pay Steele just before the election to continue investigating Trump's ties to Russia.

"Jim is walking into a political firestorm," Michael Hayden, the former director of the CIA and the National Security Agency, told CNN on Wednesday morning of Comey. Hayden said he faced similar intense questions about his judgment from the congressional judiciary committees while he was heading the intelligence agencies.

He said his experience differed from Comey's, however, because the president he served under, George W. Bush, "always had my back."

It is unclear if Comey enjoys the same kind of support from Trump, who has criticized the high-profile FBI director for failing to recommend criminal charges against Clinton for using a private email server to conduct government business while she was secretary of state.

The FBI was among the US intelligence agencies that concluded in January that Russia interfered in the election to help Trump win — an assessment Trump views with deep skepticism.

On Tuesday night, Trump tweeted that Comey gave Clinton "a free pass for many bad deeds," raising questions about why he asked Comey to stay on as FBI director when he took office in January. Five days before the inauguration, Trump's chief of staff, Reince Priebus, said Trump "has confidence" in Comey.

"We have had a great relationship with him over the last several weeks," Priebus said, calling Comey "extraordinarily competent."

Two days after he was inaugurated, Trump greeted Comey with a hug and a smile during a reception for law enforcement at the White House.

"He's become more famous than me," Trump said jokingly.