Gun-control advocates in Florida are mobilizing behind an ambitious aim: to pass a ban on semiautomatic rifles with high-capacity magazines for the first time in a Republican-controlled state.

Promoting the effort are survivors and relatives of victims of the 2018 school shooting in Parkland, Fla., that killed 17 people and the 2016 Pulse nightclub shooting in Orlando, Fla., that killed 49. A political committee they formed, Ban Assault Weapons Now, is pushing to meet a February deadline to gather enough signatures to put a proposed constitutional amendment on the 2020 ballot.

“Passing a ban on assault weapons in Florida will set an example that it is absolutely possible for other states to follow suit, no matter their political affiliation,” said Al Hoffman, a Republican donor and one of the founders of Americans for Gun Safety Now, which has contributed $260,000 to the campaign.

It faces significant obstacles. The signature-gathering process in Florida is onerous, and the ballot language must be approved by a state Supreme Court that leans conservative. Florida also has historically supported few gun restrictions and is home to one of the National Rifle Association’s most powerful lobbyists, Marion Hammer.

Semiautomatic rifles like the AR-15 and AK-47 have been used in many of the deadliest mass shootings in the U.S., including in Parkland, Orlando and Las Vegas, where a gunman opened fire on a concert crowd in 2017, killing 58 people. They also have figured in recent shootings, like one in El Paso, Texas, in August that killed 22.