WASHINGTON — Willie Nelson headlines a concert for Rep. Beto O’Rourke later this month, and the joint appearance will put a spotlight on one of the more contentious issues in the Senate race: pot.

Whatever else the country music legend has in common with the El Paso Democrat seeking to oust Sen. Ted Cruz, they share a strong belief that marijuana should be decriminalized.

These two performed together over the summer at Nelson's annual Fourth of July picnic. O'Rourke joined Nelson on stage to perform pro-pot tunes such as "Roll Me Up and Smoke Me When I Die" and "It's All Going to Pot."

O’Rourke pushes the marijuana issue at just about every campaign appearance. Cruz regularly warns his own supporters about his opponent’s stance.

Unlike a growing list of states such as Colorado and California, Texas has resisted legalization. But public opinion has shifted and many Texans might be surprised at how many of their neighbors are open to the idea.

Seven things to know ahead of the Sept. 29 concert in Austin:

1. O'Rourke's position

O’Rourke has been an advocate for decriminalizing marijuana and keeping it out of the hands of children. He argues that minorities have suffered the brunt of enforcement, adding to the urgency of ending the era of prohibition.

"Who's going to be the last black man to be behind bars in Texas for something that's legal in the rest of the United States?" O'Rourke asked at a Richardson town hall last month, a stance he expresses at nearly every campaign stop. "We need to end the war on drugs that's become a war on people."

O'Rourke advocates for expunging the records of people convicted of relatively minor charges of possession of marijuana. Those criminal records, he argues, prevent people from finding work, finishing their education and contributing to society. To press the point, he speaks openly of his own arrest history — for drunken driving and burglary — and how fortunate he was that the cases were dismissed and he was able to move on.

"A school-to-prison pipeline has produced the largest prison population on the face of the planet," O'Rourke said at a rally at the Texas Capitol last month.

In May, the political action committee of the National Organization for the Reform of Marijuana Laws endorsed O'Rourke.

"Beto has been a true champion for abolishing our disastrous prohibition on marijuana since the very beginning of his political career as a city council member in El Paso," the group said.

2. Cruz strongly opposes legalization

Cruz has accused O'Rourke of pushing to legalize not just marijuana but all narcotics. The allegation stems from a comment the Democrat made during his time on the El Paso City Council, and he has disavowed that stance.

With opioids ravaging so many American communities, Congressman Beto O’Rourke's radical resolution to legalize all narcotics—including heroin and other deadly opioids—is looking worse and worse all the time: https://t.co/VdwaYMccMn #TXSen — Ted Cruz (@tedcruz) May 1, 2018

Cruz has argued that decisions over whether to ban or decriminalize marijuana should be left to each state — and said that he would oppose legalization in Texas.

Willie Nelson launched a line of Willie's Reserve cannabis with his album "Last Man Standing."

3. Nelson doesn't just use marijuana. He's a major promoter.

When Jimmy Carter was president, Nelson famously smoked a joint on the roof of the White House.

His songs about marijuana include “It’s All Going to Pot” with Merle Haggard. The music video published on April 20, which is considered a day of celebration for cannabis culture and advocates for marijuana. It shows Nelson lighting up a joint and passing it back and forth with Haggard.

“Roll Me Up and Smoke Me When I Die” is another Nelson classic.

Roll me up and smoke me when I die

And if anyone don't like it, just look 'em in the eye

I didn't come here, and I ain't leavin'

So don't sit around and cry

Just roll me up and smoke me when I die

He is the face of the NORML advisory board. Other celebrities on the board include actor Woody Harrelson and comedian Bill Maher.

In 2015, Nelson launched his own brand of cannabis called Willie's Reserve, with sales initially in Colorado, Washington, Nevada and Oregon.

"For a long time, I've thought it should be legalized," Nelson told The Associated Press last year. "Now different states are starting to do it, and next thing you know maybe a lot more states will do it."

4. What the polls say

An April Quinnipiac University Poll found that 61 percent of Texas voters approve of allowing adults to legally possess small amounts of marijuana for personal use. That's only slightly lower than the 63 percent of voters nationally who support legalizing possession for personal use.

5. The Trump administration's position

The Trump administration has shown little interest in liberalizing the nation's marijuana laws. In March 2017, Attorney General Jeff Sessions defended the ongoing war on drugs, arguing for ongoing criminal enforcement, treatment and prevention. He called marijuana dependency only "slightly less awful" than heroin dependency.

That brought a sharp rebuke three months later from Nelson, who told The Washington Post that Sessions' comparison is flat-out wrong. He seemed to speak from experience.

“Try heroin and try marijuana and then call me and let me know if he still thinks it's the same thing and one is as bad as the other,” Nelson said.

6. O’Rourke also has taken the attorney general to task

In Jan. 2018, after Sessions announced that federal prosecutors could decide for themselves whether to press marijuana cases in states that have legalized its use, O'Rourke said: "We've absolutely got to end the federal prohibition on marijuana to allow any state, including Texas, to make its own decision."

We're not going to let Jeff Sessions drag us backwards. His decision on marijuana is terrible policy. pic.twitter.com/LxwWwBkid4 — Beto O'Rourke (@BetoORourke) January 5, 2018

7. Nelson’s fondness for marijuana has led to run-ins with the law

Nelson was arrested in Dallas in 1974 for marijuana possession.

His latest arrest happened in 2010 when 6 ounces of marijuana were discovered on his tour bus during a routine checkpoint in Sierra Blanca, Texas. Nelson was was briefly held and released after paying the $2,500 bond.

And he’s had plenty of scrapes in between.

In May 1994, two highway patrol officers found Nelson sleeping in the back of his car just off Interstate 35 south of Waco. He had played a late night of poker in Hillsboro and got tired on his way back to Austin, so he pulled over to nap. They spotted a joint in the ashtray and he admitted he had a bag of pot under the driver's seat. The charges were later dropped.

On Sept. 18, 2006, Nelson and others on his bus were arrested at a commercial vehicle inspection station in Louisiana while traveling from Alabama to Austin for the funeral of former Texas Gov. Ann Richards. Authorities found one and a half pounds of marijuana and an eighth of a pound of hallucinogenic mushrooms.

Nelson said the contraband belonged to him and was for his personal use. He was fined $1,024 and given six months’ probation.