Retired Lt. Gen. Michael Flynn may have stepped down as national security adviser, but the scrutiny over his communications with Russia is just beginning.
"There are questions about what, if any, contacts Gen. Flynn had with the [Russian] ambassador prior to the election," said Sen. Mark Warner of Virginia, the senior Democrat on the Senate Intelligence Committee, in an interview hours before Flynn's resignation. "These are legitimate questions and legitimate inquiries that I think Americans need to know."
Flynn is one of several figures close to President Trump who can expect to face tough questions in the Senate as an Intelligence Committee investigation begins looking into Russian meddling before Election Day, Warner told ABC News.
"Nothing about this resignation or resignations that could occur in the future precludes the Senate Intelligence Committee from continuing to investigate Gen. Flynn or any other campaign official who may have had inappropriate and improper contacts with Russian officials prior to the election," Warner said in a statement released on Tuesday.
Warner and the Republican Intelligence Committee Chairman Richard Burr late Tuesday pledged a cooperative effort in investigating the question of Russian meddling.
"We are aggressively going to continue the oversight responsibility of the committee," Burr said, "including any contact by any campaign individuals that might have happened with Russian government officials."
Their comments came after the committee members met behind closed doors and, sources told ABC News, began compiling a list of names of potential witnesses. Whether Flynn would be called to testify remains unknown, but Burr did not rule it out. "We won't exclude that," he said.
In the House, leading Democrats said they are looking to broaden their probe into allegations of Russian meddling during the campaign season.
"We in Congress need to know who authorized his actions, permitted them and continued to let him have access to our most sensitive national security information despite knowing these risks," said Rep. Elijah Cummings of Maryland, the ranking Democrat on the House Oversight and Government Affairs Committee. "We need to know who else within the White House is a current and ongoing risk to our national security."
A Cummings aide told ABC News the congressman has asked for a full classified briefing by all relevant agencies, including the Department of Justice and the FBI within 48 hours. Cummings officials said they are monitoring reports of a Pentagon investigation into payments Flynn received for a 2015 speaking engagement in Moscow that led him to be seated at dinner next to Russian President Vladimir Putin.
Trump's team has said emphatically there was no communication between his campaign and the Kremlin or its agents. In January, during the transition period, then-Vice President-elect Mike Pence appeared on Sunday talk shows to address the question head on. "Of course not," he said on Fox News when asked about communications with Russia. "Why would there be any contact between the campaign? This is all a distraction, and it's all part of a narrative to delegitimize the election and to question the legitimacy of [Trump's] presidency."
The White House has not commented on the propriety of Flynn's conversations with the Russian ambassador. Tuesday morning, Kellyanne Conway, counselor to the president, told ABC News' George Stephanopoulos, "I don't know all the details."
House Speaker Paul Ryan also declined Tuesday morning to answer detailed questions about the matter.
"I think we need to get all of the information before we prejudge anything," he said.
Warner told ABC News he believes both political parties want to "get to the bottom" of questions about possible Russian influence during the 2016 campaign.
"And the one thing that I'm finding that gives me heart here - the one thing I found on this subject is that the vast majority of senators in both parties want us to get to the bottom of this," Warner said.
Top Dems want wider Flynn-Russia probe