Updated, 7:30 p.m. Tuesday: with Beto O'Rourke's rally near the University of Texas at Austin

AUSTIN — While U.S. Sen. Ted Cruz has aired ads questioning his Democratic opponent’s support for less punitive drug laws, Congressman Beto O’Rourke isn’t backing down.

On Tuesday, O’Rourke repeated his call for decriminalizing the possession and sale of small amounts of marijuana.

And the three-term U.S. House member linked current pot laws to what he described as too many arrests of students, a trend he said foolishly stunts young lives at a stiff cost to taxpayers.

“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.

Children as young as kindergartners are being discriminated against because of race, resulting in discipline, suspension and expulsion, he said.

Youthful prisoners are “doing time right now for nonviolent drug charges, including possession of marijuana — a substance that is legal in 29 states in this country today,” he said.

He said arrest records for people convicted of marijuana possession should be expunged.

O’Rourke also called for changes to the cash bail system, saying high bail amounts disproportionately keep poor Texans behind bars before they’re convicted of a crime.

More than 100 people endured triple-digit temperatures to attend the afternoon rally. It was organized by Austin-area criminal-justice activists who said in an internet post that they want to end "mass incarceration" and privately run prisons, as well as raise the age for criminal responsibility to 18 from 17. Many attendees wore black and white "Beto" shirts, commemorating the event's biggest-name speaker.

During his speech, O’Rourke bemoaned Texas’ low rate of voter participation. He said some people believe "that their vote doesn't count as much as someone else's, that their voice is not intended to be heard, and so they're staying home right now."

.@TedCruz also has a new TV ad contrasting his work on unemployment drug testing with @BetoORourke's 2009 comments about the war on drugs (Background: https://t.co/cLxvNdigIs). #txsen pic.twitter.com/leVOnazXaN — Patrick Svitek (@PatrickSvitek) August 3, 2018

Earlier this month, Cruz ran a 30-second TV spot that assailed O’Rourke for his views on drugs. Cruz noted he recently helped pass a law that allows drug tests for laid-off workers seeking unemployment benefits.

“But Beto O’Rourke said we should consider legalizing all narcotics, including heroin,” a narrator in the Cruz ad says.

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

As an El Paso City Council member in 2009, O’Rourke called for an "honest, open national debate on ending the prohibition on narcotics." He tried to pass a nonbinding resolution calling for such a dialogue, though it failed to pass.

O’Rourke didn’t call for legalizing all narcotics, though he later admitted to having been confused in thinking in 2009 that marijuana — his major concern — was a narcotic.

O’Rourke hasn’t made pot legalization a major plank of his Senate campaign, though he doesn’t hesitate to say that the federal prohibition should end. He says the money spent on prosecuting and incarcerating people for marijuana offenses would be better spent on higher teacher pay or treating opioid and methamphetamine addiction.

After the event Tuesday, O'Rourke held a campaign rally near the University of

Texas at Austin that was geared toward encouraging young people to vote. He spoke about how his college years at Columbia University shaped him.

"Any important changes will not come from people like me, already in a position of power," he told the crowd of mostly students. "[Change] almost always comes from young people."

CORRECTION, 1:54 p.m., Aug. 29, 2018: An earlier version of this story quoted O'Rourke as saying it was irrational for people to conclude that their votes don't count, but a campaign spokesman said O'Rourke said it was rational because the system has led them to believe that.