Susan Davis

USA TODAY

WASHINGTON — Warning: Increased voter turnout could be a political side effect of marijuana.

The latest George Washington University Battleground poll, a national survey of likely voters, reveals that nearly four in 10 respondents say they would be "much more likely" to vote if marijuana legalization issues were on the ballot. An additional 30% say such ballot initiatives would make them "somewhat" more likely to vote.

The numbers are encouraging to Democratic pollster Celinda Lake, who conducted the survey with GOP pollster Ed Goeas, because Democrats historically have a tougher time than Republicans in turning out voters in non-presidential election years.

The GWU survey underscored the enthusiasm gap going into 2014 elections: 64% of Republicans say they are extremely likely to vote this year, compared with 57% of Democrats. Among young voters, who are a pillar of the Democratic base, 36% said they are extremely likely to vote.

"Which is why you can imagine we're very excited about our marijuana numbers in this poll, not only for personal consumption to get through this election, but in terms of turnout," Lake quipped.

Support for legalizing medical marijuana use has grown steadily with 73% in favor, while a majority, 53%, also back decriminalizing marijuana possession, according to the survey.

"What's really interesting and, I think, a totally unwritten story is that everyone talks about marriage equality hitting a tipping point (of acceptance). Marijuana is hitting the tipping point. It's really astounding about how fast it's moved," Lake said.

The issue is also motivating beyond traditional political lines. For example, in the successful push for a 2012 Colorado ballot initiative to legalize recreational marijuana use, supporters mobilized libertarian-leaning Republicans by running ads on country-music radio stations that reached the state's rural areas.

Lake says the data show that the most ardent opponents to legalizing medicinal marijuana use are seniors, while suburban moms are reluctant to support the decriminalization of possession. Both groups historically turn out in midterm elections in higher frequency than young adults.

So far this year, only two states have approved marijuana ballot initiatives. In Alaska, voters will decide whether to follow Colorado and Washington and regulate and tax marijuana like alcohol, which in effect would legalize recreational usage. The measure appears on the Aug. 19 primary ballot because the state does not allow initiatives on the general election ballot. That ballot will also settle a hotly contested GOP primary for the U.S. Senate.

Florida voters in November will decide whether to allow for medicinal marijuana use, which would require a supermajority of voters, 60%, to enact. November's Florida gubernatorial election is likely to be among the most competitive races in the nation this year.

In Oregon, the state Legislature declined to put the issue on the November ballot but activists are considering a petition effort to circumvent that decision and get a vote on a legalization measure similar to Colorado's on the ballot this fall.

More than a dozen other state legislatures are mulling marijuana laws.

The Marijuana Policy Project plans to support a number of ballot initiatives to regulate marijuana like alcohol in Arizona, California, Massachusetts, Maine, Montana and Nevada, but those initiatives won't be ready until 2016.