Former Secretary of Housing and Urban Development Julián Castro and former Rep. Beto O’Rourke (D-Texas) got into a heated argument during Wednesday’s Democratic primary debate over the topic of immigration.

Castro began the conflict during his answer to a question about immigration. The former HUD secretary brought up Section 1325 of the Immigration and Nationality Act which has been used to criminalize illegal immigration, calling for it to be replaced by a system of civil penalties. “Let’s be very clear, the reason that they are separating these little children from their families is that they are using section 1325 of that act, which criminalized crossing over the border, to incarcerate the parents and then separate them,” Castro said. He then targeted O’Rourke by name, saying, “Some of us on this stage have called to end that section, to terminate it, some, like Congressman O’Rourke, have not.”

Before allowing O’Rourke to respond, Castro continued by saying, “And I want to challenge all of the candidates to do that. I just think it is a mistake, Beto, and I think if you truly want to change the system then we have to repeal that section. ”

O’Rourke was then able to get in his response to Castro, turning to the fellow Texas Democrat and asserting, “Actually, as a member of Congress, I helped to introduce legislation that would ensure we don’t criminalize those who are seeking asylum and refuge in this country.” He continued to defend his previous refusal to decriminalize illegal immigration, stating that the law was necessary to punish those trafficking drugs and people.

Castro fought back, pointing out that there were other sections of the Immigration and Nationality Act that covered traffickers, so there was no need for Section 1325. He ended the argument with one final jab at O’Rourke, saying, “I think you should do your homework on this issue, if you did your homework on this issue you would know we should repeal this section.”

The two candidates have been taking shots at each other for months as both politicians attempt to become the dominant Democrat from Texas. Castro previously held that position, with many viewing him as a rising star, maybe even the next Obama. But O’Rourke’s massively popular 2018 Senate campaign brought him into the public eye, displacing Castro as the Democratic jewel of the Lone Star state. Now the two are circling each other, trying to outdo one another and win the vote of groups close to their heart, such as Latinos.

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