Former Trump campaign chairman Paul Manafort (L) arrives at a federal courthouse with his attorney Kevin Downing, November 2, 2017 in Washington, DC.

Paul Manafort, President Donald Trump's former campaign manager, heads to federal court in Washington Friday morning, facing the very real risk of being sent to jail that same day.

Manafort faces arraignment on charges of witness tampering filed last week by special counsel Robert Mueller.

The judge in the case will also hear arguments by Mueller that Manafort's $10 million bail should be revoked or modified because of that alleged tampering.

Manafort, who was already facing serious criminal charges, is now also accused of trying to influence a potential trial witness while under house arrest.

That witness was connected to a lobbying group that worked on behalf of ex-Ukrainian President Viktor Yanukovych, the special counsel's court filing said.

Mueller claims Manafort recently sent the potential witness an encrypted message. Manafort allegedly was trying to get the witness to agree with his story that the lobbying group "worked in Europe."

In reality, both men knew the group also worked in the United States without having registered as representatives of a foreign government, as was legally required, according to Mueller.

Manafort's Russian associate Konstantin Kilimnik has also been charged with knowingly trying to influence or prevent witnesses' testimony.

Manafort's lawyers have denied he did anything improper.

Manafort has been charged in several indictments with acting as an unregistered foreign agent, lying to investigators and conspiracy to launder money, among others.

Those alleged crimes relate to Manafort's consulting work on behalf of a pro-Russia political party in Ukraine.

Manafort has pleaded not guilty to all charges.

Mueller's team has so far issued indictments against a total of 20 people and entities as part of its investigation of Russian interference in the 2016 election.

Manafort's status in the Trump campaign and connections to pro-Russian political parties in Ukraine have made him a central figure in the probe.

Manafort also attended a June 2016 Trump Tower meeting with Donald Trump Jr. and a Kremlin-linked Russian lawyer, in which the younger Trump was promised damaging information about Democratic presidential nominee Hillary Clinton.

That meeting reportedly has become a focus of Mueller's probe into whether the president, who drafted a misleading public statement about the meeting, obstructed justice.

Mueller's investigation to date has collected five guilty pleas — including one from Manafort's longtime associate Rick Gates.

Gates was also involved in Trump's campaign and had been accused of many of the same charges still facing Manafort.

Gates agreed to cooperate with the special counsel after pleading guilty to conspiracy against the United States and to lying to investigators.