Demonstrators gather outside the White House Wednesday to protest President Trump's dismissal of FBI Director James Comey.Jonathan Ernst / Reuters

President Trump’s stunning ouster on Tuesday of FBI Director James Comey, who told Congress in March he was investigating whether the president’s campaign colluded with Russian intelligence officials, catapulted the ongoing probe into Russian electoral interference back onto the national stage.

According to the administration, Trump fired Comey for his controversial actions last year during the FBI investigation into Hillary Clinton’s private email server, including both his June press conference castigating her actions and his October letter to Congress that some believed cost her the presidency. But Democrats and some Republicans immediately criticized the decision and demanded an independent investigation.

At the core of the “Russia investigation”—a phrase often used as shorthand in news reports—is the FBI probe itself. Traditionally, the bureau does not comment on ongoing investigations except in unusual circumstances. But the probe’s existence was widely reported even before Comey publicly confirmed it in March; it had reportedly began last July. Its scope is expected to be broad, covering the cyberattacks targeting Democratic political infrastructure last year as well as the dissemination of stolen emails from the Democratic National Committee and Clinton campaign chairman John Podesta.

Those acts fall well within the FBI’s role as the premier American counterintelligence agency. Comey also made a more explosive revelation in his March appearance before Congress: that federal investigators are also looking into “the nature of any links between individuals associated with the Trump campaign and the Russian government, and whether there was any coordination between the campaign and Russia’s efforts.” Trump, as well as those who worked in his campaign’s orbit, have strongly denied any wrongdoing.

A key focus in that avenue of the FBI investigation is believed to be Michael Flynn, the former national-security adviser fired by Trump in February. In January, The Wall Street Journal reported federal investigators interviewed Flynn about his conversations with Sergey Kislyak, the Russian ambassador to the United States, on the same day in December that the Obama administration announced sanctions against Russia for its interference in the election. His denials about the conversations eventually led to his ouster. After leaving the post, Flynn filed papers to register as a foreign agent for lobbying work he performed on behalf of the Turkish government in mid-2016, months before Trump named him as his national-security adviser.

That work, plus payments he received from a Russian state-run media outlet in 2013, apparently drew law-enforcement scrutiny. CNN reported Tuesday that federal prosecutors in eastern Virginia issued subpoenas to Flynn associates on the subject as part of a grand jury investigation—a sign that at least part of the FBI’s Russia probe is in advanced stages. The U.S. attorney’s office in the Eastern District of Virginia frequently prosecutes national-security cases; it’s unknown whether other U.S. attorney’s offices are involved, too.

Another FBI target is Carter Page, a one-time Trump campaign adviser on foreign-policy issues. Page joined the campaign in March 2016 and traveled to Moscow that July to give a commencement address at the New Economic School. While there, Page said he didn’t speak with any Russian officials under U.S. sanctions. But the trip apparently caught the bureau’s attention. Federal investigators reportedly applied for a FISA warrant targeting Page’s communications at some point after the Moscow trip, suggesting they believed they had probable cause he was aiding a foreign power in some way. Page has denied any wrongdoing.

The FBI isn’t the only federal agency involved. The Journal reported that Flynn is also under investigation by two U.S. foreign-intelligence agencies, the Central Intelligence Agency and National Security Agency, as well as the Treasury Department, which has a financial-crimes division. McClatchy reported in January that a similar slate of agencies is examining the extent of Moscow’s financial efforts to influence the election.

In addition to the FBI’s sprawling work, both the House and Senate intelligence committees have launched inquiries of their own. On Wednesday, the Senate’s committee also subpoenaed Flynn for documents that he had previously declined to share with the committee. Of the two, the House’s investigation has received the most attention—and not for good reasons. It began fairly well under Republican Chairman Devin Nunes and Democratic Ranking Member Adam Schiff, with both members vowing to examine the extent of Russian influence in the election.

Things fell apart in March when Nunes, without consulting his fellow committee members, made a dramatic announcement on the White House lawn that “on numerous occasions the intelligence community incidentally collected information about U.S. citizens involved in the Trump transition.” The White House touted his opaque statement as partial validation for Trump’s disproven claim that his predecessor Barack Obama had ordered wiretaps for Trump Tower. Multiple news outlets later reported Nunes had obtained this information from the White House itself. As Democratic criticism of his leadership reached a fever pitch, he stepped aside in early April amid a House Ethics Committee probe.

The Senate Intelligence Committee’s investigation has largely avoided the public drama of its House counterpart. Richard Burr, the committee’s Republican chairman, said Tuesday night he was “troubled by the timing” of Comey’s firing. Comey was reportedly a key ally of the committee, who briefed the members on important classified information as its inquiry proceeded.

Burr and Mark Warner, the committee’s Democratic ranking member, invited Comey to testify before the committee in an open hearing on Thursday. That could be the public’s first opportunity to hear from the former FBI director on his stunning downfall—the latest twist in an investigatory saga that appears to be far from over.

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