Next week is the 2018 midterms where Democrats are looking to retake control of Congress to slow down the Trump administration's agenda. But many believe it is also an important election for marijuana legalization. So it's probably a good time to figure out which members of Congress are most impeding that progress.

Kris Krane is a co-founder of a cannabis investment and management firm, 4Front. He and his team looked at members of Congress to determine who are the most supportive and the most combative towards marijuana legalization. And now Krane and his team have determined the five worst U.S. senators on marijuana policy.

It should be noted they used a number of factors to make these determinations, including voting records, public statements, committee positions and more. Here were who they deemed the worst:

1. Richard Shelby (R – Alabama)

Shelby recently became the chairman of the Senate Appropriations Committee and has used that power to prevent nearly every marijuana amendment from reaching a vote. He claims this is simply a byproduct of his fiscally conservative views, but he's also voted against every single piece of marijuana reform that's reached the Senate in recent years. Unfortunately he's not up for re-election until 2022.

2. Mitch McConnell (R – Tennessee)

McConnell is the most powerful man in the Senate as the Majority Leader, so he basically makes the agenda. And that agenda has not included marijuana. While he does support legalizing hemp farming, he's firmly maintained that he opposes any sort of marijuana legalization.

3. Dianne Feinstein (D – California)

That's right, there are Democrats on this list as well. This is more of a historical distinction however. Feinstein has been probably the most anti-marijuana Democrat ever, and has opposed every single marijuana legalization effort in her home state of California. But after years of taking heat on this issue, Feinstein finally this year endorsed legalization. But it remains to be seen if it's just lip service or an actual change of heart.

4. Ted Cruz (R – Texas)

Cruz is a strange case. On one hand, he bashed President Barack Obama for not cracking down on Colorado when the state legalized recreational marijuana. Then when he ran for president in 2016, suddenly he supported states making their own decisions. However while he may say he supports states making their own decisions, he's failed to support any piece of legislation that could remotely help them do so.

5. Tom Carper (D – Delaware)

Yep, Carper's another Democrat with a long history of vocally opposing marijuana. He's one of the few Democrats to receive an F rating on the issue from marijuana reform organization NORML. Like Feinstein, Carper also changed course and said he supported legalization this year when he faced a tough challenge in the Democratic primary against another pro-cannabis Dem. But we'll see if Carper actually decides to stick to his word.

(h/t Forbes)