If Donald Trump were to fire Special Counsel Robert Mueller there would surely would rush to preserve the documents in his Russia probe, while legislators would demand a special congressional committee to continue his investigation.

Democrats have reportedly already prepared for any attempt to remove Mr Mueller from the federal investigation into Russian election meddling and possible collusion with trump campaign officials, drafting a contingency plan with specific measures to address both immediate and long term consequences.

The same has been done for the possible firing of Deputy Attorney General Rod Rosenstein, who oversees the investigation.

Chris Coons, a Delaware Democrat and member of the Senate Judiciary Committee, revealed in an interview with NBC News that Democrats would immediately begin contacting a list of "sympathetic Republicans" who have indicated they would reject the Special Counsel’s firing if it were ever to happen.

"We’ve had a lot of conversations about how exactly and who and when and where," he said. "There have been several moments when it seemed imminent."

Almost a year ago, congressional aides to House Minority Leader Nancy Pelosi and Senate Minority Leader Chuck Schumer began collaborating on a “ playbook” to address what would happen in a variety of scenarios in which Mr Mueller could be fired.

Donald Trump calls Paul Manafort 'a good man' following eight counts of bank and tax fraud

Those aides worked alongside top Democrats on the Judiciary Committee and oversight panels, NBC News reported.

The scenarios and their various outcomes are reportedly outlined in great detail: if the announcement of Mr Mueller’s firing were to arrive before 2:00 p.m. in Washington, demonstrations would be scheduled for 5:00 p.m. that same day. If the announcement was made in the late afternoon, the protests would arrive the next day at midday.

Those would occur alongside massive demonstrations already planned by progressive groups outside of the halls of Congress: already, 350,000 people have RSVP’d to a potential event organised by MoveOn.org, which has prepared at least 933 rallies from Los Angeles to North Dakota and beyond.

Mr Trump has signalled that he could end the Russia investigation if he chooses to, either by firing Mr Mueller himself or firing Mr Rosenstein, setting off a chain of events that may allow him to install a deputy attorney general willing to axe the Special Counsel.

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In recent weeks, the president has appeared to have grown even further frustrated by the investigation, telling Reuters in an interview on Monday that he’s “totally allowed to be involved” in the investigation in any way he pleases.

"I could run it if I want," Mr Trump added.

Still, it remains unclear how the Republican Party would response in the event of Mr Mueller’s firing. In their contingency plan, Democrats have drafted language for letters to be sent to committee chairmen and White House counsel Don McGahn, as well as the Justice Department. Those letters would demand information into their own communications with the president and White House prior to Mr Mueller’s firing, essentially paving the way for a new series of investigations into obstruction of justice.