WASHINGTON (AP) — Lawyers for Donald Trump asked a judge Thursday to dismiss the Washington federal election subversion case against him, arguing the Republican is immune from prosecution for actions they say were taken in his official role as president.

The motion amounts to the most pointed attack yet by defense lawyers on the federal case charging Trump with plotting to overturn the results of the 2020 presidential election he lost to Democrat Joe Biden. It tees up a fight over the scope of presidential power, forcing courts to wrestle with whether the actions Trump took in his failed bid to remain in office fell within his duties as commander-in-chief or whether they strayed far outside his White House responsibilities and are subject to prosecution.

“Breaking 234 years of precedent, the incumbent administration has charged President Trump for acts that lie not just within the ‘outer perimeter,’ but at the heart of his official responsibilities as President,” the defense motion states. “In doing so, the prosecution does not, and cannot, argue that President Trump’s efforts to ensure election integrity, and to advocate for the same, were outside the scope of his duties.”

The presidential immunity argument had been foreshadowed for weeks by defense lawyers as one of multiple challenges they intended to bring against the indictment.

Special counsel Jack Smith’s team is expected to vigorously contest the motion. It is not clear when U.S. District Judge Tanya Chutkan might rule, but potentially protracted arguments over the motion — including an expected appeal if she denies the request — could delay the case as courts step into what defense lawyers described an unsettled question.

The Supreme Court has held that presidents are immune from civil liability for actions related to their official duties. But Trump’s lawyers noted in their motion that no court has addressed the question of whether that immunity shields a president from criminal prosecution, hinting that the defense will likely fight the issue all the way to the nation’s highest court.

“In addressing this question, the Court should consider the Constitution’s text, structure, and original meaning, historical practice, the Court’s precedents and immunity doctrines, and considerations of public policy,” they wrote.

Prosecutors appeared to anticipate the immunity argument, writing in the indictment that though political candidates are permitted to challenge their election losses and to even falsely claim victory, Trump’s actions strayed far beyond what is legally permissible in the run-up to the Jan. 6, 2021, riot at the U.S. Capitol, when pro-Trump rioters stormed the building to disrupt the counting of electoral votes.

In their motion, defense lawyers argue that the actions that form the basis of the indictment, including urging the Justice Department to investigate claims of voter fraud and pressing state officials on the administration of elections, cut to the core of Trump’s responsibilities as commander in chief.

The Justice Department has held that sitting presidents cannot be prosecuted. The motion Thursday seeks to ensure that same protection to a former president for actions taken while in office, asserting that no prosecutor since the beginning of American democracy has had the authority to bring such charges.

“Every action of the Defendant charged in the indictment occurred while he was still in office as President of the United States, and, according to the prosecution, all concerned a federal government function,” they wrote. “Given the all-consuming nature of the Presidency, these facts alone strongly support the notion that the indictment is based solely on President Trump’s official acts.”

They contend that Trump’s tweets and public statements about fraud in the election and Vice President Mike Pence’s role in the certification were directly related to his assertion that the election’s outcome was tainted by fraud and that the Justice Department and certain states had failed to adequately investigate it.

And they say meetings detailed in the indictment with Justice Department officials also fall within his official duties because he was urging his agency “to do more to enforce the laws that it is charged with enforcing.”

Prosecutors alleged a broad range of criminal conduct in a four-count indictment issued Aug. 1, accusing Trump of conspiring with a half-dozen allies to pressure state officials to alter the results of their elections; enlist slates of fake electors in battleground states who could falsely claim that Trump had won; and persuade Pence to shirk his duty to certify the vote count before Congress.

The indictment says Trump knew the claims he was pushing about election fraud were false but did so anyway in an effort to undermine the integrity of the democratic process. But Trump’s lawyers say “the president’s motivations are not for the prosecution or this Court to decide.”

Trump’s lawyers also argue his 2021 impeachment trial acquittal bars his prosecution, saying the Constitution suggests presidents can only be criminally charged in cases where they are impeached and convicted by the Senate.

“President Trump was acquitted of these charges after trial in the Senate, and he thus remains immune from prosecution. The Special Counsel cannot second-guess the judgment of the duly elected United States Senate,” his lawyers wrote.

The case, one of four Trump is facing, is currently set for trial on March 4, 2024.

His lawyers have separately sought the dismissal of a New York state case charging him with falsifying business records in connection with hush money paid to a porn actress who alleged an extramarital affair with Trump years earlier.

In court papers made public late Wednesday, Trump’s lawyers accused prosecutors of reviving a so-called “zombie case” to interfere with his comeback campaign for the White House and argued that Manhattan District Attorney Alvin Bragg, a Democrat, only brought the case because of politics.

Defense lawyers also sought late Wednesday to postpone until after the 2024 presidential election the trial in a separate criminal case in Florida charging him with illegally hoarding classified documents.