TALLAHASSEE — Abortion rights advocates spent months, and millions of dollars, gathering petition signatures so Florida voters could decide if they want abortion to be protected now that Roe v. Wade has been overturned.

They got the measure on the Nov. 5 ballot, and hundreds of thousands of Floridians voting by mail already have said yes or no to Amendment 4, the abortion question.

But an 11th-hour lawsuit filed Wednesday by anti-abortion opponents threatens to derail their efforts. The lawsuit, heavily based on a report from Gov. Ron DeSantis’ administration and pushed by his allies, alleges “widespread fraud” in the abortion petition drive and seeks to strike Amendment 4 from the ballot — or nullify any election results.

After so much effort and time, could Amendment 4 really go by the wayside, regardless of what the voters want? It seems at least possible, according to experts interviewed by the Orlando Sentinel — a suggestion that deepens the extraordinary political and legal morass into which the abortion rights measure has been cast.

Opponents can tap into case law that provides a “veritable blueprint” for challenging a ballot initiative based on fraud accusations, said Bob Jarvis, a law professor at Nova Southeastern University.

Jarvis’ views are echoed by other experts who note Florida case law allows such challenges, even after an election. But the lawsuit faces tough hurdles, they say, from proving widespread fraud to overcoming other legal questions.