Today is 4/20, the holiday for marijuana enthusiasts around the world.

More Americans are likely to celebrate 4/20 today than ever before. Cannabis sales reportedly skyrocketed just before the coronavirus pandemic began locking down most of the country. One survey similarly showed that marijuana use reached records heights last month.

Marijuana has even become a winning political issue, with a remarkable rise in public support for legalization over the past two decades. Two-thirds of Americans back legal recreational use, up from one-third 20 years ago.

But the political benefits of running on legalization extend beyond that. Legalization is popular in swing states and among swing voters. It’s also one of the only policies that is important to voters across the political spectrum. Together, those facts make marijuana an especially potent campaign issue.

Most voters in every state support marijuana legalization

Recreational marijuana use for adults over the age of 21 is legal in only 11 states, but marijuana legalization has broad support throughout the country.

The map above shows that a majority of voters in every state supports legalization. Over the past three years, the polling firm Civiqs has asked 140,000 registered voters their opinions about legal cannabis. Scrolling across the map shows those results by state. You can see by doing so that statewide support for legalization ranges from about 55 percent in North Dakota to about 79 percent in Oregon and Washington.

More importantly, the map shows that marijuana legalization is also popular in the handful of battleground states that will determine who wins the 2020 presidential election. Swing-state support for legal cannabis ranges from a low 65 percent in Minnesota to a high of 67 percent in New Hampshire.

Undecided and third-party voters support legal cannabis

Marijuana isn’t just popular in swing states. It’s also popular with swing voters. We can look at how small, but potentially pivotal, groups feel about legalization in the UCLA/Nationscape data, an enormous academic survey that has interviewed more than 200,000 registered voters since the summer of 2019.

The graph above shows public opinion about marijuana legalization among undecided 2020 voters, third-party voters from 2016 and pure independents who don’t lean toward one of the two major parties.

As you can see, independent and undecided voters support marijuana legalization by more than a 2-to-1 margin. Americans who voted for Gary Johnson and Jill Stein in 2016 — third-party candidates who both made marijuana legalization central to their presidential bids — even more strongly support legalizing cannabis.

Marijuana legalization is important to voters

It’s one thing to say that voters support legalizing marijuana. It’s quite another to say they would actually vote for a presidential candidate based on this policy.

Americans rarely vote for president based on a single issue. Voters are much more likely to change their opinions about significant campaign issues based on their previous opinions about the candidates than they are to change their votes based on the candidates’ positions on issues.

Nevertheless, a few issues arouse so much passion that candidates’ positions sometimes matter. Opinions about immigration policy, for example, strongly predicted voting for candidates from different parties in the 2012 and 2016 presidential elections.

Marijuana legalization appears to be one of these strongly held, gut-level issues, too. Political science research from the 1970s found that Americans as a whole held stronger views about marijuana than just about any other public policy.

A much newer study also shows that marijuana legalization is one of the more important issues to voters. To better understand voter priorities, political scientists Lynn Vavreck, John Sides and Chris Tausanovitch embedded a series of innovative “conjoint experiments” into the UCLA/Nationscape survey. The experiments forced voters to decide repeatedly from among random collections of policy outcomes. Those repeated choices revealed the relative importance of more than 50 prominent issues.

When Vavreck and colleagues presented their results, they showed a clear pattern: Marijuana legalization was not only popular across the political spectrum, but it was also one of the more important issues to Democrats, Republicans and independents.

Of course, legalizing marijuana was not as important to voters as the most polarizing issues of the day, such as impeachment and the border wall. But it was a more important priority to voters than any of the fiscal issues that dominate so much political debate, such as taxes and health care, especially among pure independents who do not lean toward either party.

Implications for 2020

To be sure, the popularity of marijuana legalization and its importance to many voters would only matter in a close 2020 election. Most voters are already locked into their choices, given how polarized party supporters are and how strongly Americans feel about President Trump.

But the data still suggest that Joe Biden is missing a big political opportunity to run on legalization in a presidential campaign in which Democrats face an uphill battle in the electoral college. Although Biden’s position on marijuana policy is more lenient than Trump’s, he remains opposed to full legalization in the United States.

Biden has repeatedly defended his position on legal cannabis by saying that the policy’s impact still needs to be studied. The political impact, however, is unambiguous: Marijuana legalization is a winning campaign issue.