Virginia Sen. Mark Warner, the top Democrat on the Senate intelligence committee, met with Facebook officials in California more than a month ago as part of his committee's investigation into potential collusion or election interference, and he's convinced the company can explain whether anyone from the Trump campaign helped Russians boost fake news articles targeting Democratic presidential nominee Hillary Clinton. Warner is testing the theory popular among Democratic operatives that Russia was behind spikes in fake news that were anti-Clinton and that Russia had help targeting those articles from US political operatives.
"If the Russians know, how are the Russians smart enough to target in areas where the Democrats weren't knowledgeable enough? I don't feel like I have run that to ground yet," Warner told CNN.
"There are two questions. One is: Was there coordination or collusion between the campaigns and these technology tools, which overwhelmed the search engine tools so that certain stories popped up at the top of your newsfeed. The second is, on a broader basis going forward: How do we prevent this from happening again?" Warner said.
Likewise, House investigators plan to interview former Trump campaign digital director Brad Parscale as part of their probe. A Democratic committee source said they want to know whether Parscale or anyone else from the campaign helped guide Russian targeting of fake news stories.
Parscale, who announced last week he would testify before the House, and other Trump campaign digital staff have denied this allegation, saying they are unaware of any Russian activity.
Trump's digital staff have said the best way to clear their names is for Facebook to testify.
A digital staffer who worked with the Trump campaign, Gary Coby, said Facebook would know exactly what the Trump campaign was doing -- and that the campaign was not coordinating with Russian operatives -- because Facebook staff worked side by side with the Trump digital campaign staff.
But both the Democrats and Trump's digital staff are likely to face a tough battle trying to get answers from Facebook, which has previously fought government requests citing personal privacy and free speech concerns.
"We've been in touch with a number of government officials, including Sen. Warner, who are looking into the 2016 US Presidential election," a Facebook spokesman told CNN. "We will continue to cooperate with officials as their investigations continue. As we have said, we have seen no evidence that Russian actors bought ads on Facebook in connection with the election," a reference to a line of inquiry Warner is investigating.
At the core of Warner's questioning is a theory among Democratic operatives and former top-level Clinton campaign staff that Russia had help from domestic political operatives to micro-target fake news articles. No evidence has been uncovered to prove that theory.
Last month, Senate intelligence staff interviewed Brett Horvath, a social media technology expert who argues it's possible that Russian operatives got political data that could then be used for successfully micro-targeting swing voters on Facebook.
"Facebook has all the data that could prove this is happening or not happening, that's the starting point," Horvath, a veteran Democratic political operative, told CNN.
"The tech companies, the vendors as we call them, all had people assigned to help us. Google, Twitter and Facebook," said Coby, who was working with the Trump campaign as part of the Republican National Committee's support team.
"Since we were spending so much with Facebook we worked with the Facebook team the most," Coby said. "We were starting from scratch and welcomed all the help we could get."
Another Trump campaign digital staffer said that there is no evidence to prove the theory popular among Democrats, but said that only Facebook can answer three critical questions: were the same databases used by the Trump campaign and Russian operatives to coordinate targeting of voters; was money used to promote pro-Trump posts, and, if so, how much was spent and by whom; and will Facebook reveal if bots were successfully used to push fake news posts?
"Those three questions answer everything," the second Trump campaign staffer said.
But Facebook has had some rocky battles with the members of the Senate intelligence committee in the past. Senate Intelligence Committee Chairman Richard Burr, a North Carolina Republican, and Sen. Dianne Feinstein, a Californian who at that point was the top Democrat on the committee, fought Facebook in 2015 to try and force the company to report suspected terrorist activity to law enforcement.
"They told us to pound sand," Burr said of the intelligence committee's efforts on ISIS recruiting posts. Facebook argued that it would infringe on privacy and free speech rights of its users, but it also said Facebook "Shares the government's goal of keeping terrorist content off our site."
Republicans on the House and Senate intelligence committees have been generally dismissive of most Democratic theories -- but on the Senate side, a few have shown interest in the proliferation of fake news. In a May hearing, Florida Sen. Marco Rubio expressed concerns about the explosion of fake news in general and wanted answers on how it spread.
In the immediate wake of the election, Facebook CEO Mark Zuckerberg was dismissive of the impact of fake news, but has since supported efforts to counter fake news. In the French elections, Facebook took down 30,000 fake accounts.
And Facebook's own internal review by its security team, released earlier this year, determined that "malicious actors" created fake accounts on their platform to spread misinformation during the campaign. But it also pointedly did not name who was responsible for the fake news posts.
Asked what he would do if Facebook does not have the detailed information on fake news, Warner said he wasn't sure.
"That's a great question and I don't have the answer to that," he said. "I've got a lot more questions to get answered."