A U.S. judge dismissed one of Donald Trump’s criminal cases on Monday, handing the Republican presidential candidate a major legal victory just hours before he was due to reveal his vice presidential running mate.

A Trump-appointed judge issued the decision two days after the former president survived an assassination attempt at a Pennsylvania campaign rally by a gunman whose motive remains unknown.

U.S. District Court Judge Aileen Cannon ruled that the prosecutor who charged Trump with mishandling classified documents was unlawfully appointed to his role.

Trump was expected to formally announce his vice presidential pick at the 2024 Republican National Convention in Milwaukee, according to a source who spoke on condition of anonymity.

Republicans will nominate the candidate around 4:30 p.m. ET (2030 GMT), though Trump could reveal his pick before then.

Leading contenders include Ohio U.S. Senator J.D. Vance, Florida U.S. Senator Marco Rubio and North Dakota Governor Doug Burgum, all of whom are due to speak at the four-day convention this week. Rubio has been told he will not be chosen, according to three sources speaking on condition of anonymity.

Trump is due to formally accept the party’s nomination on Thursday to challenge Democratic President Joe Biden in the Nov. 5 election.

Trump, 78, and Biden, 81, are locked in what opinion polls show to be a tight election rematch. Trump continues to falsely claim that his 2020 loss to Biden was the result of widespread fraud and has not committed to accepting the results of the election were he to lose.

In the wake of the assassination attempt, Trump said he is revising his acceptance speech to emphasize national unity, rather than highlight his differences with Biden.