(CNN) President Donald Trump has expressed concern that he could be impeached when Democrats take over the House, a source close to the President told CNN Monday. The source said Trump sees impeachment as a "real possibility."

But Trump isn't certain it will happen, the source added.

A separate source close to the White House told CNN that aides inside the West Wing believe "the only issue that may stick" in the impeachment process is the campaign finance violations tied to former Trump attorney Michael Cohen's payouts to Trump's alleged mistresses.

Impeachment talk has ratcheted up in recent days following a blockbuster filing from prosecutors in the Southern District of New York. In that filing, prosecutors directly alleged for the first time that Cohen was being directed by Trump when he broke the law during the 2016 presidential campaign.

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