The outcome of the arguments carries enormous ramifications both for the landmark criminal case against Trump and for the broader, and legally untested, question of whether an ex-president can be prosecuted for acts committed in the White House. It will also likely set the stage for further appeals before the U.S. Supreme Court, which last month declined a request to weigh in but could still get involved later.

A swift decision is crucial for special counsel Jack Smith and his team, who are eager to get the case — now paused pending the appeal — to trial before the November election. But Trump’s lawyers, in addition to seeking to get the case dismissed, are hoping to benefit from a protracted appeals process that could delay the trial well past its scheduled March 4 start date, including until potentially after the election.

Underscoring the importance to both sides, Trump intends to attend Tuesday’s arguments even though the Iowa caucuses are just one week away and despite the fact that there’s no requirement that defendants appear in person for such proceedings. It will be his first court appearance in Washington, one of four cities where he faces criminal prosecutions and potential trials, since his arraignment in August.

He’s already signaling that he could use the appearance to portray himself as the victim of a politicized justice system. Though there’s no evidence that President Joe Biden has had any influence on the case, Trump’s argument could resonate with Republican voters in Iowa as they prepare to launch the presidential nomination process.

“Of course I was entitled, as President of the United States and Commander in Chief, to Immunity,” he wrote in a social media post, adding, “I was looking for voter fraud, and finding it, which is my obligation to do, and otherwise running our Country.”

Former presidents enjoy broad immunity from lawsuits for actions taken as part of their official White House duties. But because no former president before Trump has ever been indicted, courts have never before addressed whether that protection extends to criminal prosecution.

Trump’s lawyers insist that it does, arguing that courts have no authority to scrutinize a president’s official acts and decisions and that the prosecution of their client represents a dramatic departure from more than two centuries of American history that would open the door to future “politically motivated” cases. They filed a similar motion on Monday in another criminal case against Trump in Georgia.

Smith’s team has said presidents are not entitled to absolute immunity and that, in any event, the acts Trump is alleged in the indictment to have taken — including scheming to enlist fake electors in battleground states won by Biden and pressing his vice president, Mike Pence, to reject the counting of electoral votes on Jan. 6, 2021 — fall far outside a president’s official job duties.

“Immunity from criminal prosecution would be particularly dangerous where, as here, the former President is alleged to have engaged in criminal conduct aimed at overturning the results of a Presidential election to remain in office beyond the allotted term,” Smith’s team wrote in a brief.

“A President who unlawfully seeks to retain power through criminal means unchecked by potential criminal prosecution could jeopardize both the Presidency itself and the very foundations of our democratic system of governance,” they added.

Prosecutors say that if Trump’s view of the law were to be accepted, a president could get away with steering a lucrative government contract in exchange for a bribe; instructing the FBI director to plant incriminating evidence on a political enemy; or selling nuclear secrets to a foreign adversary.

The case is being argued in the U.S. Court of Appeals for the D.C. Circuit before Judges J. Michelle Childs and Florence Pan, both appointees of President Joe Biden, and Karen LeCraft Henderson, who was named to the bench by former President George H.W. Bush.

It’s not clear how quickly the panel will rule, though it has signaled that it intends to work fast. The judges requested that both prosecutors and defense lawyers submit briefs in rapid succession last month, including setting filing deadlines on Saturdays.

U.S. District Judge Tanya Chutkan, who is presiding over the case, rejected the Trump team arguments, ruling on Dec. 1 that the office of the presidency does not confer a “‘get-out-of-jail-free pass.’” Trump’s lawyers appealed that decision, but Smith’s team, determined to keep the case on schedule, sought to leapfrog the appeals court by asking the Supreme Court to fast-track the immunity question and rule in the government’s favor. The justices declined, without explanation, to get involved.

The appeal is vital to a broader Trump strategy of trying to postpone the election subversion case until after the November election, when a victory could empower him to order the Justice Department to abandon the prosecution or even to seek a pardon for himself. He faces three other criminal cases, in both state and federal court, though the Washington case is scheduled for trial first.

Trump’s lawyers have also cited a constitutional provision against double jeopardy in arguing for immunity, saying that the case concerns similar conduct for which he has already been impeached by the House of Representatives but acquitted by the Senate.

Smith’s team has said there’s no bar against prosecutors charging someone who’s been impeached and acquitted in the Congress, and note their charges are not identical to the ones that Trump faced in his impeachment proceedings.