A little over a year after Colorado and Washington legalized marijuana, more than half the states, including some in the conservative South, are considering decriminalizing the drug or legalizing it for medical or recreational use. That has set up a watershed year in the battle over whether marijuana should be as available as alcohol.

Demonstrating how marijuana is no longer a strictly partisan issue, the two states considered likeliest this year to follow Colorado and Washington in outright legalization of the drug are Oregon, dominated by liberal Democrats, and Alaska, where libertarian Republicans hold sway.

Advocates of more lenient marijuana laws say they intend to maintain the momentum from their successes, heartened by national and statewide polls showing greater public acceptance of legalizing marijuana, President Obama’s recent musings on the discriminatory effect of marijuana prosecutions and the release of guidelines by his Treasury Department intended to make it easier for banks to do business with legal marijuana businesses.

Their opponents, though, who also see this as a crucial year, are just as keen to slow the legalization drives. They are aided by a wait-and-see attitude among many governors and legislators, who seem wary of pushing ahead too quickly without seeing how the rollout of legal marijuana works in Colorado and Washington.