Washington: The scandal over Russian meddling in last year's presidential election returns to the forefront of Washington politics after weeks of quiet on Monday, when two top officials from the Obama administration are set to testify in Congress.
Sally Yates -- acting attorney general in the Trump administration for 10 days before being fired -- could bring new pressure on the White House over what it knew about former national security advisor Michael Flynn's communications with Russian officials.
Obama's director of national intelligence James Clapper is also set to testify, after repeatedly warning of the need to get to the bottom of how the Russians interfered in the election, and whether anyone on President Donald Trump's team colluded with Moscow.
The case has simmered for weeks as attention focused elsewhere on what keynote legislation the president could push through in his first 100 days, reached on Sunday.
Congressional investigations into the matter have also been held up by infighting between Democrats and Republicans over how aggressively to pursue a matter that continues to cast a cloud over Trump's election win.
Trump this week repeated his dismissal of US intelligence chiefs' conclusion that Moscow had sought to boost his campaign over his Democratic rival Hillary Clinton's in an effort overseen by Russian President Vladimir Putin.
In an interview with CBS's "Face the Nation" program marking his 100 days, Trump again rejected the official view that Russians hacked Democratic Party computers and communications.
"(It) could have been China, could have been a lot of different groups," he said. On Tuesday, he again branded the whole story as fake. "The phoney Trump/Russia story was an excuse used by the Democrats as justification for losing the election," he said on Twitter.
Trump's dismissals notwithstanding, the Senate Judiciary Committee -- where Yates and Clapper appear on Monday -- and the House and Senate Intelligence Committees are stepping up their probes, calling numerous current and former government witnesses to testify, mostly behind closed doors.
And the FBI continues its own active investigation into possible collusion. The country's top intelligence officials have no doubt Moscow tried to swing the election against Clinton last year through hacking and disinformation.
Nor is there any doubt that people closely associated with the Trump campaign -- including Flynn, onetime foreign affairs advisor Carter Page and campaign chairman Paul Manafort -- all had ongoing contacts with Russians.
But whether those contacts resulted in any collusion with Moscow remains unproved. Asked on CNN this week if she had yet seen any evidence of collusion in private intelligence briefings, Senator Diane Feinstein, the top Democrat on the Senate Intelligence Committee, responded: "Not at this time."
In Monday's hearing, Yates -- an Obama deputy attorney general who was fired by Trump for refusing to support his immigration ban -- reportedly could testify that she warned the incoming administration in January that Flynn's discussions with Russia's US ambassador left him vulnerable to blackmail.
A former military intelligence chief, Flynn was Trump's national security advisor for 24 days before he was fired for lying about the substance of the calls.
Clapper, still bound by secrecy requirements of his former job, might not add more than what the intelligence community has already said publicly about the scandal.
The more serious investigative action in the coming weeks will take place out of the public eye. The House and Senate intelligence committees are holding interviews with current intelligence and Trump campaign officials behind closed doors.
The Senate side has warned possible witnesses, including Flynn, Page and Manafort, that they could be subpoenaed to testify if they do not voluntarily cooperate with the probe, according to the New York Times.
In a statement Friday, the top senators on the Senate committee specifically warned Page, a former Moscow-based investment banker, to meet their week-old request for specific documents.
"Should Mr Page choose to not provide the material requested" by specified dates, they said, "the committee will consider its next steps."