The Las Vegas Democrat has sponsored or signed onto bills and amendments that would protect state laws from Justice Department interference, allow marijuana businesses to use banks and let military veterans access medical cannabis recommendations through government doctors, among others.

Those measures haven't advanced, however, because of roadblocks thrown up by Congressional Republican leadership.

But even though the GOP-controlled House Rules Committee won't allow floor votes on marijuana amendments, and Speaker Paul Ryan hasn't done anything to help, Titus said in an interview that cannabis isn't just an issue for Democrats.

"This was not partisan," she says of the measures she has supported. "It was heavily Democratic but we had Republicans supporting these amendments. I think if they came to the floor they would pass."

Indeed, large bipartisan majorities approved floor amendments to protect state medical cannabis laws from federal interference in 2014 and 2015, but since then House leadership has consistently prevented votes.

Titus says that "Republicans aren't going to buck their leadership and sign a discharge petition" to circumvent committees and force measures to the floor, but she is hopeful that shifting poll results on legalization and the growing number of changing state laws will make Congress come around soon.

"We're going to keep on beating the drum, and I think you reach a tipping point because every cycle there are more initiatives and more efforts by state legislatures to legalize marijuana in some fashion. It's over half of the states that have it now," she says. "So when public opinion shifts...and more states make it legal, then the Republicans are going to have to respond."

Titus believes it is important that she tailor her pitch when trying to convince fellow members of Congress to support cannabis legislation.

"You make the argument based on who you're talking to," she says. "Some believe it's a criminal justice issue. Others believe it's a states' rights issue. Others see it as a medical opportunity issue. You've got a few who are just old stoned hippies who want to do it."