PORTLAND — Nationally-backed and Maine-based marijuana activists are uniting behind a push in Maine to legalize marijuana and plan to work together to put the measure on the statewide ballot, they said Monday.

The nationally backed Campaign to Regulate Marijuana Like Alcohol will stop collecting signatures in support of an initiative it filed in March and will work on behalf of a similar initiative by Legalize Maine with a goal of collecting of about 61,000 valid signatures of registered Maine voters to get on the 2016 ballot.

“This is a major milestone on the path to ending marijuana prohibition in Maine. Either of these campaigns could be successful on their own, but together we can put our best feet forward in 2016,” said Paul McCarrier, president of Legalize Maine.

The Campaign to Regulate Marijuana Like Alcohol is backed by the Washington-based Marijuana Policy Project, while Legalize Maine is a homegrown effort. Both groups had collected about 40,000 signatures, they said.

The groups are trying to seize upon momentum to legalize recreational use of marijuana in Maine after victories in Portland and South Portland in 2013 and 2014 respectively.

“Joining forces is the best step forward, not only for our respective campaigns, but for Maine as a whole. We all agree marijuana prohibition has been a colossal failure,” said David Boyer, manager of the Campaign to Regulate Marijuana Like Alcohol, who led efforts on behalf of the Marijuana Policy Project in South Portland and Portland.

Both want to create a taxed, government-regulated marijuana industry.

But there were differences in the proposals. For example, Legalize Maine’s proposals would create “marijuana social clubs” and allow cultivators to sell directly to consumers.

Rep. Diane Russell of Portland, a proponent of marijuana legalization, said the differences are small and are likely to be tweaked by lawmakers if the referendum is approved.

“Right now the differences are pretty small. By the time it shakes out through the sausage-making process it’ll be robust, fleshed out policy,” she said.