When California voters weigh in Nov. 8 on whether to legalize retail and/or online sports betting, their decision will cap what is expected to be the costliest initiative campaign in U.S. history. And if experts in politics and sports betting are right, the hundreds of millions spent may all have been for naught.

As the calendar turned this month to the final 100 days ahead of the midterm elections, the already bitter initiative campaigns turned vitriolic. And those backing “No” campaigns have been hammering voters in their ads with negative statistics, comments, and other messages on a nearly daily basis.

Last week alone, media consultants from multiple “No” campaigns issued releases announcing that homelessness advocates, teachers groups, and legislative leaders on both sides of the aisle oppose a proposition backed by commercial operators.