BOSTON >> Some of the state's top political leaders are backing a committee formed to oppose legalized recreational marijuana in Massachusetts.

The group calling itself A Campaign for a Safe and Healthy Massachusetts plans to file papers on Thursday with the state Office of Campaign and Political Finance, which will allow it to raise money to fight a measure likely to appear on the November state ballot.

Republican Gov. Charlie Baker and Democrats including House Speaker Robert DeLeo and Boston Mayor Marty Walsh are among those supporting the effort to stop marijuana legalization.

The opponents released a statement saying that Colorado, the first state to allow recreational pot, now has more marijuana shops than McDonald's and Starbucks combined.

Supporters of the proposed ballot question dismissed what they called "reefer-madness, scare-tactic arguments."