MEXICO CITY -- This may not weigh heavily on the minds of voters in Seattle, but if Washington and two other U.S. states decide to legalize marijuana in next week's election, the effect on drug traffickers in Mexico could be enormous.

Such is the suggestion of a new study by a Mexican think tank.

"It could be the biggest structural blow that (Mexican) drug trafficking has experienced in a generation," Alejandro Hope, security expert with the Mexican Competitiveness Institute, said in presenting the report.

Producing and distributing marijuana inside the U.S. would supply a less expensive and better quality drug to the millions of American who smoke it, Hope said.

Demand for Mexican pot would decline, cutting into cartels' profits by 22 percent to 30 percent, the study calculates.

The consequences would be most dramatic, Hope said, for the powerful Sinaloa Cartel, which is based in western Mexico and controls most of the marijuana production.

It is estimated that around one-third of Mexican drug gangs' income is from marijuana, surpassed only and narrowly by cocaine.

Washington, Oregon and Colorado have legalization initiatives on their ballots. Hope cited polls that showed likely approval for the measure in Washington and Colorado and defeat in Oregon.

Taking into account taxes, markups, transportation costs and other factors, U.S.-produced marijuana would retail at a little more than half the cost of illegally shipped Mexican pot, Hope's study indicated.