Maine Democrats do not have to look far for a primer on what it is like to replace a deeply flawed nominee forced off the ballot weeks before a deadline to be stuck with him.

Two Julys ago, former President Joseph R. Biden Jr. succumbed to political reality following his debate meltdown and ended his re-election bid. Party officials had just two weeks to choose a replacement.

Now that Graham Platner has removed his name from the Maine Senate ballot before Monday’s deadline, after a rape allegation that he denies, the state party’s officials have to find a new candidate and convince voters that the selection process was fair.

Recent history suggests neither task is easy. The 2024 anointment of Vice President Kamala Harris left a trail of hurt feelings and second-guessing that has not stopped and political scars that have yet to heal.

“It would be really awesome if they didn’t Kamala Harris us,” said Michael Rowell, 45, a Democrat of Sullivan, Maine. “A lot of people were disappointed by the way they handled that transition.”

Last-minute switches are difficult, said Jaime Harrison, who in 2024 was the Democratic National Committee chairman who oversaw the transition from Mr. Biden to Ms. Harris. “The reality and the expectations people have are not the same, and that creates a lot of issues for the Maine Democratic Party now, just like at the D.N.C. two years ago.”