Congress will grill two top U.S. intelligence officials on Monday in a bid to pin down details of Russian contacts with President Donald Trump's campaign and inner circle, and refute Mr. Trump's seemingly baseless accusation that the Obama administration spied on him during the campaign.
FBI Director James Comey and National Security Agency Director Mike Rogers will appear before the House of Representatives Intelligence Committee in the first open hearing of the panel's investigation into Russia's attempt to tip last year's election to Mr. Trump.
The FBI established in January that Russian President Vladimir Putin's regime hacked into the Democratic Party's servers and released embarrassing e-mails through WikiLeaks in a bid to undermine the party's presidential nominee, Hillary Clinton.
Subsequent leaks to media from inside the government have shown at least two of Mr. Trump's people – former national security adviser Mike Flynn and Attorney-General Jeff Sessions – spoke with Russia's U.S. Ambassador, Sergey Kislyak.
But so far, no one has shown a connection between such contacts and the Russian hacking. Congressmen want to know if the intelligence agencies have found any link.
"Were there U.S. persons who were helping the Russians in any way? Was there any form of collusion?" Representative Adam Schiff, the top Democrat on the committee, said on NBC's Meet the Press Sunday.
The extent of Russian influence on the election – and the ties to Mr. Trump's people – has been the most nagging unanswered question of his two-month-old administration.
Mr. Flynn spoke with Mr. Kislyak in late December, shortly after then-president Barack Obama imposed new sanctions on Russia and expelled diplomats. Following the conversation, the Kremlin made the surprise announcement that it would not retaliate for Mr. Obama's moves.
Mr. Sessions, for his part, met with Mr. Kislyak in September at the height of the presidential campaign, in which Mr. Sessions was serving as a surrogate for Mr. Trump. But at Mr. Sessions' Senate confirmation hearing, he claimed he was "not aware" if anyone from Mr. Trump's campaign had any contact with the Russians.
Mr. Trump fired Mr. Flynn for initially claiming he had not discussed sanctions with Mr. Kislyak when it later emerged that government wiretaps of the ambassador's telephone had in fact recorded the pair discussing the sanctions. Mr. Sessions has kept his job after claiming he had not fully understood the question during the Senate hearing.
The session with Mr. Comey and Mr. Rogers will likely broach Mr. Trump's accusation that the previous administration wiretapped Trump Tower during the campaign. The President has provided no evidence to support his claim and even fellow Republicans have conceded there is none.
But the Democrats may be tempted to press the matter and force the intelligence officials to confirm publicly that no such surveillance of the Trump campaign took place.
The Republicans, for their part, are likely to deflect attention from Mr. Trump by pushing for information on the leaks of intelligence information to U.S. media that brought to light contacts between Mr. Trump's circle and Russian officials. The President has repeatedly complained about anonymous sources in government handing over intelligence information to reporters, and Republican committee chair Devin Nunes echoed this on Sunday.
"The one crime we know that's been committed is that one: the leaking of [Mr. Flynn's] name … That's what we're trying to get to the bottom of," he said on Fox News Sunday. "Were there any other names that were unmasked, leaked?"
Whether Mr. Comey and Mr. Rogers will answer any of these questions in much detail is another matter. If they are in the middle of an active investigation into the Trump-Russia links, they may be hesitant to share details.
Mr. Comey, in particular, has already frustrated legislators of both parties by being surprisingly open at times, then clamming up at others.
Eleven days before the election, he informed Congress that he was reopening an investigation into Ms. Clinton's e-mails, then abruptly closed it a few days later. The move drew anger from Democrats, who blamed Mr. Comey for hurting their campaign right before the vote.
Last week, Republican senators said they weren't getting prompt answers from Mr. Comey on whether his agency has investigated Mr. Trump.
Republican Senator Chuck Grassley threatened to stall the confirmation of the deputy attorney-general if Mr. Comey continued to duck requests to brief the Senate judiciary committee.
"We were not given the respect that the Constitution gives us of oversight of the executive branch of government," he told CNN. "That's very irritating."
Both the House and the Senate are conducting investigations into the Russian election interference. The House has scheduled a second day of testimony for next Tuesday.
Several other key players may testify, including ex-CIA director John Brennan, former director of national intelligence James Clapper and Sally Yates, the former acting attorney-general who informed the White House of Mr. Flynn's discussions with Mr. Kislyak.
In addition to the public hearings, the House and Senate committees are also reviewing documents and receiving closed-door briefings. They will ultimately issue reports detailing their findings.