WASHINGTON (AP) — Special counsel Jack Smith asked a federal judge on Monday to dismiss the case accusing President-elect Donald Trump of plotting to overturn the 2020 election, citing longstanding Justice Department policy shielding presidents from prosecution while in office.

The move announced in court papers marks the end of the Justice Department’s landmark effort to hold Trump accountable for what prosecutors called a criminal conspiracy to cling to power in the run-up to his supporters’ attack on the U.S. Capitol on Jan. 6, 2021.

Justice Department prosecutors, citing longstanding department guidance that a sitting president cannot be prosecuted, said the department’s position is that “the Constitution requires that this case be dismissed before the defendant is inaugurated.”

“That prohibition is categorical and does not turn on the gravity of the crimes charged, the strength of the Government’s proof, or the merits of the prosecution, which the Government stands fully behind,” the prosecutors wrote in Monday’s court filing.

The decision was expected after Smith’s team began assessing how to wind down both the 2020 election interference case and the separate classified documents case in the wake of Trump’s victory over Vice President Kamala Harris. The Justice Department believes Trump can no longer be tried in accordance with longstanding policy that says sitting presidents cannot be prosecuted.

Trump has cast both cases as politically motivated, and had vowed to fire Smith as soon as he takes office in January.

The 2020 election case brought last year was once seen as one of the most serious legal threats facing the Republican as he vied to reclaim the White House. But it quickly stalled amid legal fighting over Trump’s sweeping claims of immunity from prosecution for acts he took while in the White House.

The U.S. Supreme Court in July ruled for the first time that former presidents have broad immunity from prosecution, and sent the case back to U.S. District Judge Tanya Chutkan to determine which allegations in the indictment, if any, could proceed to trial.

The case was just beginning to pick up steam again in the trial court in the weeks leading up this year’s election. Smith’s team in October filed a lengthy brief laying out new evidence they planned to use against him at trial, accusing him of using “resorting to crimes” in an increasingly desperate effort to overturn the will over voters after he lost to President Joe Biden.