Watch FBI Director James Comey's testimony above.
WASHINGTON – UPDATES: FBI Director says he thought concealing discovery of new Clinton emails before election would have been `catastrophic'
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The top Democrat on the House intelligence committee says FBI Director James Comey's explanation for why he disclosed details about the Hillary Clinton email investigation is a "poor characterization" of the choice.
Rep. Adam Schiff, of California, said Comey's decisions to talk publicly about the Clinton probe and not say anything about the Trump investigation was a violation of FBI policy.
Comey told the Senate Judiciary committee that he acted consistently when he disclosed to Congress that the bureau was investigating new material related to the Clinton email probe, yet did not disclose last year that the FBI was investigating President Donald Trump's campaign and possible coordination with the Russians.
FBI Director James Comey will testify Wednesday on the Capitol Hill, the day after both the sitting US President and the 2016 Democratic presidential nominee sharply criticized him for his role in the outcome of last year's presidential election.
"FBI Director Comey was the best thing that ever happened to Hillary Clinton in that he gave her a free pass for many bad deeds! The phony......Trump/Russia story was an excuse used by the Democrats as justification for losing the election. Perhaps Trump just ran a great campaign?" President Donald Trump said in a pair of tweets Tuesday.
Senate judiciary Chairman Chuck Grassley originally called the Wednesday oversight hearing of the FBI to examine what the agency knows about a 2015 terrorist attack in Garland, Texas. His interest is based on media reports that an undercover FBI agent was in contact with the two perpetrators of the attack and was present when it happened.
But the broad oversight hearing is expected to quickly shift to the FBI's investigation into Russian meddling in the US elections, a subject on which there are four congressional probes in progress and from which there have been a steady stream of revelations since President Donald Trump was elected.
Most recently, CNN reported Tuesday that former acting Attorney General Sally Yates is prepared to testify before a Senate panel next week that she gave a forceful warning to the White House regarding then-national security adviser Michael Flynn and his conversations with the Russians nearly three weeks before he was fired, contradicting the administration's version of events.
Comey has become an almost equally divisive figure for Republicans and Democrats for his impact on the 2016 elections. His revelation that the FBI was examining additional emails from Hillary Clinton that were discovered on disgraced former Rep. Anthony Weiner's computer, has led Democrats -- including Clinton herself -- to say it cost them the White House.
"I was on the way to winning until a combination of Jim Comey's letter on October 28 and Russian WikiLeaks raised doubts in the minds of people who were inclined to vote for me and got scared off," the 2016 Democratic presidential nominee said Tuesday in an interview conducted by CNN's Christiane Amanpour at the Women for Women International summit in New York.
Senate Democrats say the plan to grill the FBI chief about his decision and his timing.
"The most important investigation the FBI is currently conducting is into Russia's interference in our last presidential election," Sen. Chris Coons, a Delaware Democrat on the Senate judiciary committee, told CNN Tuesday. "This isn't just about understanding Russian interference and potential coordination of some kind with the Trump campaign. This is about defending our next election as well."
But Comey's public announcement during the March House Intelligence Committee hearing that the FBI has been investigating possible coordination between the Trump campaign and Russian operatives since last July sparked the anger of Trump and his allies.
Sen. Richard Blumenthal, a Connecticut Democrat on the judiciary committee, said he and others also plan to grill Comey on why he announced that the FBI was looking again at Clinton's emails -- just days before the election.
"The American people really deserve answers about why he did release his comments and letter, and I think he may want to be more forthcoming and he may want to use this forum as an opportunity to tell the American people his side of the story."
Meanwhile, Sen. Lindsey Graham, who is leading his own investigation into Russia's interference in the election, said he still wants Comey to answer whether the FBI issued any warrants against the Trump campaign -- a question he asked months ago.
"I just want an answer. I just want to know what is going on here," Graham said Tuesday. "You had (former Director of National Intelligence James) Clapper say there was no surveillance of the Trump campaign or Trump Tower. You've got press reports a FISA warrant was issued for Carter Page because of his ties to Russia. I just want to know what happened. And if we can't do it in an open session, let's do it in a closed session."
Wednesday's meeting will be the first of two consecutive hearings for Comey this week. The second will be a closed-door meeting with the House Intelligence Committee, focused largely on follow-up questions from their explosive first meeting in March.