With pot on the ballot in nine states, the big winner in next Tuesday's election could be America's legal cannabis industry. By 2020, legal market sales are expected to surpass $22 billion. And for states struggling with budget shortfalls, that extra revenue would be clearly welcome.

Voters in five states — Arizona, California, Maine, Massachusetts and Nevada — will decide whether to legalize recreational marijuana for adults. Medical marijuana is on the ballot in Arkansas, Florida, Montana, and North Dakota.

Supporters believe the marijuana measures will pass in California and Florida, and possibly several other states, because America's attitude about pot has changed significantly in the last few years.

"Legalization of cannabis is one of the greatest business opportunities of our time."

"It's well established that the majority of Americans now believe that the responsible use of marijuana by adults should not be a criminal offense," said Paul Armentano,...