President Donald Trump’s legal approach to dealing with Special Counsel Robert Mueller has reached its battle phase.

That’s how those close to the White House’s decision to bring on “wartime consigliere” Emmet Flood to the President’s legal team are describing the shake-up, which also includes the departure of Ty Cobb, known for his more conciliatory posture toward Mueller’s probe.

A “fight for the ages,” is what one Obama administration official said Flood’s hiring would usher in.

Fasten your seat belts folks. It’s war. I know Emmet—in fact, he briefed me during the Bush to Obama transition when I was coming in as special counsel & he was headed out. He’s one of the very best. This will be a fight for the ages. https://t.co/E7BjqxJGuE — Norm Eisen (@NormEisen) May 2, 2018

The shift in legal strategy comes as the negotiations over a Trump sit-down interview with Mueller’s team spilled out into the open, with the leak of the questions Trump’s lawyers believe Mueller plans to ask the President and a report that Mueller had raised the possibility of a grand jury subpoena if they couldn’t agree to a voluntary interview.

If those negotiations end in a standoff and Mueller makes good on his subpoena threat, Trump’s options would be limited, but he could buy time by asking the courts to determine the contours of his executive power as President, an area of law that is not completely settled. A court battle over whether Trump can resist a grand jury subpoena could take many months, legal scholars, former prosecutors and ex-White House attorneys told TPM.

“Provoking a confrontation is unfortunate, but I don’t see any away around it,” said Susan Bloch, a Georgetown Law professor and expert on impeachment. “One of the key pieces of evidence is whether Trump obstructed justice. That requires intent which requires talking to him. So, I’m sure Mueller would prefer to avoid a lengthy court battle … but I’m not sure he can avoid it.”

Trump’s options may come down to taking the Fifth Amendment — a move with political consequences that he himself has described as a sign of guilt — or gambling in the courts, where the odds appear to tilt toward the special counsel.

There’s a reason presidents engage in protracted discussions with prosecutors seeking to interview them for high-profile investigations. Asserting the Fifth Amendment to protect oneself from self-incrimination is considered an extremely costly move politically. Though legally, asserting the Fifth could be a smart decision and not a sign of guilt, for a high-profile subject of a closely-watched investigation, the stigma is hard to shake off.

When President Bill Clinton was served a grand jury subpoena by Ken Starr in the Monica Lewinsky investigation, he agreed to be interviewed for the grand jury voluntarily and was able to negotiate some terms more favorable to him.

“It’s an amazingly politically fraught thing. The typical American thinks that anybody who takes the Fifth is guilty,” Paul Rosenzweig, who served as counsel on Starr’s investigation, told TPM. “When the president takes the Fifth, everybody is going to think that he’s guilty as sin.”

Trump himself mocked IT specialists who took the Fifth in a Hillary Clinton email-related case.

“The mob takes the Fifth,” Trump said at at 2016 campaign rally “If you’re innocent, why are you taking the Fifth Amendment?”

Trump may be able to escape some of the political fallout due to his and his allies’ unrelenting smear campaign against Mueller and the Justice Department. But legal experts and former White House attorneys were skeptical that such a move will come entirely without consequence.

“As robust as the efforts have been to delegitimize normal Department of Justice operations, the seismic activity on the political Richter scale of the president of the United States asserting the Fifth Amendment in a criminal case — I can’t even imagine it,” said Andy Wright, who served as counsel for President Obama and for Vice President Al Gore.

Before he gets to that point, Trump may see if he can get the courts to help him avoiding sitting down with Mueller.

The President could assert a range of executive privileges to try to thwart Mueller – and delay invoking the Fifth Amendment. To this point, under the direction of Ty Cobb, the White House’s legal strategy has been to cooperate with Mueller. The President’s dissatisfaction with that strategy is reportedly one of the reasons Cobb is out and Flood is in. A series of confrontations over executive privilege could wind up in the courts initially. But the ultimate confrontation seems likely to be over whether the President must abide by a grand jury subpoena.

The Supreme Court in the past has twice unanimously ruled against Presidents in similar situations. But legal experts still see, perhaps, a little bit of wiggle room for Trump to try his own luck. In United States v. Nixon, the Supreme Court said that President Nixon had to turn over subpoenaed tapes for the Watergate investigation, while in Jones v. Clinton, the Supreme Court allowed a civil lawsuit against President Clinton to proceed, despite his claim that it would be an unconstitutional burden on his presidency.

In Trump’s scenario, “the facts are different,” Rosenzweig said, but “the arguments are the same.”

“That doesn’t mean that it has to come out the same way,” he added.

University of Texas School of Law professor Steven Vladeck said that the Supreme Court hasn’t “squarely resolved the issue.”

“But, man, they put a heavy thumb on the scale of, an otherwise valid subpoena being enforceable in this context,” he said.

Litigating these questions also risks Trump losing what leverage he has in negotiations over the interview’s terms and scope.

“If you litigate all of these things, you eventually end up with clear answers to some of those questions, because the courts will be involved,” said Keith Whittington, a professor of politics at Princeton University who has written about the presidency and the court. “But that will also wind up effectively shrinking the scope of the president’s legal protections. Things we weren’t going to push on have now been pushed.”