Former prosecutor breaks down why Mueller probe’s new direction could be bad news for Mark Zuckerberg

Special counsel Robert Mueller's team has begun questioning Republican National Committee staffers about their data operation -- and a former federal prosecutor suggests that could put Facebook under new scrutiny.

Investigators are asking RNC staffers about how the GOP coordinated with the Trump campaign to target voters in key swing states, and Renato Mariotti, a Democratic candidate for Illinois attorney general and a former federal prosecutor, explained what that new direction might mean.

"This aspect of Mueller’s investigation deserves more attention, because it’s the piece most likely to result in charges that resemble what people commonly call 'collusion' — Russians and Americans working together to influence the election," Mariotti tweeted.

He said the special counsel had previous obtained a search warrant for Facebook records, which means Mueller had evidence that convinced a judge there was a "good reason a crime occurred" during the campaign.

"That crime would likely be a foreign contribution in connection with a U.S. election, which is a crime if it is done knowingly and willfully," Mariotti explained. "It’s also a crime for an American to knowingly aid in that effort."

Sen. Mark Warner (D-VA), the ranking Democrat on the Senate Intelligence Committee, wants Facebook and the Trump campaign's inner circle to reveal more about their connections to Russia, which bought ads on the social network targeted to individual voters in swing states.

"I would like to have a higher confidence (Facebook has) really done the investigation of all possible Russian [connections], and some of the Russian sites were actually ... started or activated outside of Russia but are were still controlled by them," Warner told Axios last week.

Mueller's team is now investigating whether any RNC staffers illegally coordinated with Russian efforts to sway the election toward Trump, Mariotti said -- and that could spell trouble for Facebook and its chief executive, Mark Zuckerberg.

"We don’t know yet what Mueller will find, but if he indicted an American for aiding a Russian effort to influence the election, that would be more explosive than the charges we’ve seen thus far," Mariotti said.