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As the list of states that have legalized marijuana continues to grow, New York could have a new reason to embrace cannabis: It could help save the subway.

Some state and city leaders have started to discuss the idea of making recreational marijuana legal and using the revenue to pay for badly-needed and expensive subway upgrades. The proposal could face improved odds in Albany now that Democrats have taken full control of the State Legislature for the first time in a decade.

“The biggest issue we hear about as elected officials is the state of the subway system,” Corey Johnson, the City Council speaker, said in an interview. “To be able to tie these things together is something that could be highly impactful and potentially transformative.”

The idea is still very much theoretical, but it has some prominent supporters and is being considered by a high-profile panel tasked with coming up with ways to pay for a subway overhaul. Any push to legalize marijuana in New York would have to be approved by state lawmakers and Gov. Andrew M. Cuomo.