Legalizing marijuana in Massachusetts would create thousands of jobs in a newly regulated market, snatch a lucrative business away from “gangs and cartels” and generate new tax revenues for government, according to the political director of legalization efforts in five states, including Massachusetts. During a televised interview broadcast Sunday morning, Matt Simon of the Marijuana Policy Project told WCVB-TV’s “On the Record” that he believes an initiative petition being drafted to legalize marijuana will be approved “overwhelmingly” after a debate over impacts in states where it is already legal, including Colorado and Washington.