To this point, Trump has heeded advice not to directly interfere, though a new chapter in the relationship with the probe may have begun with the appointment of Matthew Whitaker as new acting attorney general.
Several senior officials told CNN they were surprised by the criticism, and believe it could potentially jeopardize Whitaker's chances of remaining in the post if it continues to dominate headlines.
At a press conference Wednesday, Trump branded CNN reporter Jim Acosta an "enemy of the people" when he posed questions, including about the Russian Federation probe, and refused to give up the mic. Trump's advisers are privately expressing worries that special counsel Robert Mueller, who's been out of the news for the past month, has been stealthily compiling information and could soon issue new indictments or a damning final report.
When the Democrats take over the House, they are expected to launch numerous probes of Trump, his business interests and his administrations. A Justice Department spokesperson has indicated that Whitaker will be assuming the full scope of the attorney general's responsibilities-including, it would seem, direct supervision of the Mueller investigation.
"Mueller has come up to a red line in the Russian Federation 2016 election-meddling investigation that he is dangerously close to crossing", Whitaker wrote.
"It's illegal. And it means that anything Mr. Whitaker does, or tries to do, in that position is invalid", Conway wrote with former acting U.S. Solicitor General Neal K. Katyal.
"It would create a constitutional crisis if this were a prelude to ending or greatly limiting the Mueller investigation", said Senate Minority Leader Chuck Schumer (D-NY).
People all over the country subscribed to an email list that would be activated if Trump appeared to be interfering with the investigation into his campaign. Last August, Whitaker remarked that he thought the Mueller investigation had gone "too far".
"People ... across this country gathered today to say ..."
I would like to get into two of the things that you reported today.
Whitaker also laid out in a July 26, 2017, CNN appearance a hypothetical scenario in which Mueller's investigation could be stifled without him being fired.
FILE PHOTO: U.S. President Donald Trump and Attorney General Jeff Sessions stand for the national anthem at a graduation ceremony at the FBI Academy on the grounds of Marine Corps Base Quantico in Quantico, Virginia, U.S. December 15, 2017. Whitaker accompanied the tweet with his own comment to his followers: "Worth a Read". One possible tactic would be continually telling prosecutors that their requests require more work or evidence before moving to the next stage, said Jeffrey Cramer, a former federal prosecutor.
Moscow denies interfering in the 2016 election.