It’s true the next president could change Justice Department policy to have it challenge the emerging marijuana industry. So, yes, for legalization it matters who is elected president and who is appointed as attorney general. But even a hostile presidential administration can’t force states to arrest people for marijuana offenses, if a state has decided to legalize possession and sale of cannabis.

On the other hand, the United States Senate has the power and authority to either prevent the White House from interfering with state-level legalization and/or make it very difficult and costly to do so.

The current Republican-controlled Senate, for example, has taken the initiative to authorize hemp research at federal research facilities with state-level authorization. Congress has also passed legislation preventing the Justice Department from using federal funds to interfere with state-level legalization of medical marijuana.

The composition of the United States Senate is a crucial factor in both protecting recent advances in marijuana’s legalization and advancing this cause further. Despite recent Republican support for hemp and protection for medical marijuana, the GOP is historically a conservative party resistant to social change, and according to modern polling data, Republican voters display the lowest levels of support for marijuana’s legalization.

The Libertarian Party has been the strongest and most consistent supporter of marijuana’s legalization in recent history, but it is unlikely that Libertarian candidates will gain seats in the U.S. Senate any time soon. However, Rand Paul, Republican Senator from Kentucky, is a vocal supporter of drug law reform and a lifelong Liberatarian. Rand Paul deserves the support of Kentucky voters in favor of marijuana’s legalization—he has earned it.

Otherwise, the best scenario for marijuana’s legalization is for the Democrats to take control of the United States Senate, regardless of the positions of individual Democrats on marijuana’s legalization. Democrats are more accountable to supporters of legalization than Republicans are, and as such, are generally and demonstrably less hostile. The voters that Democratic candidates rely on for political support are in favor of legalization, and this means that over time, support for legalization will continue to grow among Democratic office holders.

The 2016 election provides an opportunity to elect more liberal Democratic candidates to the Senate in place of conservative Republican incumbents. The incumbents may run as moderates, but the Republican Party is a conservative party, and whatever they say to get elected, Republican senators will likely vote with their conservative colleagues.

One-third of the Senate is up for election every two years. In 2016, there will be 24 Republican and 10 Democratic Senate seats up for election. The Center for Politics at the University of Virginia provides a reliable assessment of the political status of these seats.

Eight of the 10 seats held by Democrats are considered safe seats, with high odds they will be retained (CA, CT, HI, NY, MD, OR, VT, WA).  A seat is up in Colorado, where the electorate is viewed as leaning Democratic, and Harry Reid’s seat in Nevada (Reid is retiring) is considered a toss-up.

There are 24 seats now held by Republicans. Of these, 13 are considered safe seats likely to be filled by Republican incumbents or candidates. Another four are considered likely to be filled by the GOP (IN, LA, MO, NC).  

But then, for those interested in seeing the Democrats take control of the Senate, it gets interesting. Three seats are considered leaning Republican, but vulnerable (AZ, OR and PA). Two states, Florida and New Hampshire, are considered toss-ups—either party could prevail. Two more are rated as leaning Democratic—Illinois and Wisconsin.

The Democrats can win the Senate by retaining the 10 seats they currently hold, which means in addition to keeping the safe seats, they win in Colorado and Nevada and pick up 5 seats now held by Republicans. The toss-up and Democrat-leaning races provide 4 of those 5 (FL, NH, IL, WI). Then, they need one out of the four states which are leaning Republican—Arizona, Oregon, Pennsylvania or Wisconsin.

Legalization supporters in Arizona, Colorado, Florida, Illinois, Nevada, New Hampshire, Oregon, Pennsylvania and Wisconsin can advance the cause by supporting Democratic candidates in these states. Let all candidates know where you stand on legalization and that you expect them to support it. But it will be helpful, and indeed crucial, for advancing legalization for Democrats to take control of the Senate.

Learn about the candidates, register to vote if you have not done so already, make it clear to them where you stand on the issues, and vote this November.