The 2024 Democratic national convention dates are August 19-22. There are five states that require qualified parties to certify the names of their presidential nominees earlier than September 1: California August 22; Montana August 21; Oklahoma August 22; Virginia August 23; Washington August 20.
If the Democratic Party decides to use the convention itself to choose a presidential nominee, and that process takes more than a day, there could be problems with some of the states listed above, especially Washington. In the past the Washington Secretary of State has accepted provision certification, but that might not work if there is no provisional certification. Provisional certification only works if it is possible to predict who the nominee will be.
In my opinion, the Washington state deadline is unconstitutional. Constitutional challenges to early deadlines for candidates to get on ballots are adjudicated under the principles of Anderson v Celebrezze. Lower courts must balance the harm done to voting rights by the early deadline, versus the harm done to election administration if the deadline is set aside. It seems obvious that there is no genuine state interest in deadlines as early as Washington’s. States are not required to mail their overseas absentee ballots until September 21.
Michigan requires the certification the day after the later of the party’s state or national conventions. The Michigan Democratic Party is free to have a special state convention at a late date.