Updated July 6, 2018 at 10:30 a.m.: Revised to include a tweeted comment from Sen. Ted Cruz.

AUSTIN — U.S. Rep. Beto O'Rourke joined Austin legend Willie Nelson at the annual Willie's Picnic on Wednesday night.

O'Rourke, an El Paso Democrat running for Sen. Ted Cruz's seat in the fall, tucked an "I Love You El Paso" T-shirt into his pants. Strumming a guitar, he sang "Roll Me Up and Smoke Me When I Die" — a message on brand for famous pothead Willie Nelson and O'Rourke's pro-marijuana legalization stance.

After they finished that song, Nelson shouted out, "Thank you Beto!" He kept the weed theme going as they rolled into the next song, "It's All Going to Pot."

O'Rourke strummed earnestly and steadily. A former punk rock band member, O'Rourke lists Nelson's music in his repertoire. On a road trip with U.S. Rep. Will Hurd, he and Hurd sang "On the Road Again."

Nelson dipped his toes into the political arena when he criticized the zero-tolerance policy separating families who cross the southern border illegally. He even tweeted at President Donald Trump in June from his wife's account (Nelson's sparsely used Twitter account mostly promotes his concerts and interviews).

"Hey Donald this is @WillieNelson," he tweeted. "Let's go down to a border detention center together to better understand what's happening down there?!"

Trump signed an executive order in June to keep families together at the border, but said the zero-tolerance policy would continue.

According to an Austin American-Statesman reporter, Ray Benson, the frontman for Austin band Asleep At The Wheel, played with Nelson onstage while wearing a Beto shirt.

Willie’s wearing his Willie’s Reserve T-shirt tonight. Ray Benson, playing guitar with him, is decked out in a @BetoORourke tee. — Peter Blackstock (@Blackstock360) July 5, 2018

The Statesman also reported that O'Rourke had come to introduce the fireworks at Willie's Picnic before sticking around to play with Nelson.

The Willie-Beto set ended with "I'll Fly Away." O'Rourke and Nelson hugged, shook hands and parted ways as they both left the stage.

O'Rourke's set with musical legend Nelson is just one celebrity highlight in the closely watched Texas Senate race. His opponent, Sen. Ted Cruz, eked out a one-on-one basketball victory over late night talk show host Jimmy Kimmel last month in Houston. Cruz challenged Kimmel to the game after Kimmel called him a blobfish.

Cruz's Fourth of July was spent campaigning. He waved at crowds in a Rockwall parade, and headed east to Sulphur Springs and Talco.

A wonderful evening celebrating #IndependenceDay🇺🇸 in Talco yesterday! pic.twitter.com/kQ51vbdzqB — Ted Cruz (@tedcruz) July 5, 2018

Cruz admonished O'Rourke Thursday night for not learning Toby Keith's "words of advice." The Youtube link he included in his tweet goes to a performance of country artists Toby Keith and Scott Emerick, singing about how they'll "never smoke weed with Willie again."

.@BetoORourke sings to his Travis County liberal base. Seems not to have learned Toby Keith’s words of advice: https://t.co/vVfYnLjmKm https://t.co/GXXUSAk0Z6 — Ted Cruz (@tedcruz) July 6, 2018

The song pokes fun at the potency of Nelson's marijuana. But Keith and Emerick didn't seem to take their own advice too seriously. At Nelson's 70th birthday celebration, they finished the song with the line: "We broke down and smoked weed with Willie again."