Of the two dozen Democratic presidential candidates seeking the party’s nomination, former cabinet secretary Julián Castro produced the first—and the most detailed—platform on how he would shift the course of the nation’s immigration policies if elected.

As fellow Democratic hopefuls kept their remarks on immigration almost entirely couched in their emotional reaction to the immigration crisis at the U.S. southern border, Castro demonstrated that sure-footed knowledge of the labyrinthine immigration system may be a potential winner with a Democratic audience.

“If I were president today, I would sign an executive order that would get ride of Trump’s zero-tolerance policy, the ‘remain in Mexico’ policy, and the metering policy,” Castro said. “I would follow that up in my first hundred days with immigration reform that would honor asylum claims, that would put undocumented immigrants—as long as they haven’t committed a serious crime—on a path to citizenship, and then get to the root cause of the issue, which is we need a Marshall Plan for Honduras and Guatemala and El Salvador so that people can find safety and opportunity at home instead of coming to the United States to seek it.”

In contrast, the majority of the candidates who were asked what they would do on their first day in office to fix the immigration system leaned into the emotion of the issue, without grounding responses in concrete policy proposals.

Rep. Tim Ryan of Ohio expressed anger over children in immigration detention “laying in their own snot, in three-week-old diapers that haven’t been changed.” New York City Mayor Bill de Blasio attempted to redirect anger over lost jobs from immigrants to “big corporations.”

Both Sen. Cory Booker and former Rep. Beto O’Rourke began their answers in Spanish, insisting that they would not turn back asylum seekers at the border.

Castro, the former mayor of San Antonio, Texas, did not hide his own disgust with President Donald Trump’s immigration policies.

“It’s heartbreaking,” Castro said of the death of Óscar and Valeria Martinez, a father and his young daughter who drowned earlier this week while trying to cross the Rio Grande after attempting to claim asylum. “It should also piss us all off.”

But Castro paired that emotion—and some Spanish, in which he is fluent—with policy, leaning into his extensive background on the subject of immigration with calls for an end to family separation, the proposed “Marshall Plan” for Honduras, Guatemala and El Salvador, and the so-called metering of asylum seekers, which critics say amounts to turning back those lawfully seeking refuge at the nation’s border.

Metering, Castro said, was “basically what prompted Óscar and Valeria to make that risky swim across the river… they died because of that.” The Salvadoran press has alleged that the Martinezes had presented themselves for asylum in the United States while in Mexico but attempted to cross the Rio Grande after growing impatient with the asylum process there. There is no evidence that they were turned away at the U.S. border as a result of “metering,” however.

Castro also called for the repeal of Section 1325 of the Immigration and Nationality Act, which makes it a federal offense to cross or attempt to cross the U.S. border “at any time or place other than as designated by immigration officers.”

Treating illegal crossings as a criminal rather than civil offense, Castro elaborated, has allowed the Trump administration to justify separating migrant parents from their children at the border, igniting a family separation crisis that has strained both immigrant communities and immigration enforcement to their limits.

Repeal of the section is a signature immigration policy of Castro’s—and a wedge between his platform and others on the debate stage.

O’Rourke, a fellow Texas who has opposed repealing Section 1325 because he believes it would give potential cover for human trafficking, shifted the conversation to family separation but was interrupted by Castro, who said that the issues of Section 1325 and family separation are one and the same.

“The reason that they’re separating these little children from their families is they’re using Section 1325... to incarcerate the parents and then separate them,” Castro said. He then called on the rest of the Democratic candidates on the debate stage in Miami to join him in pledging to repeal Section 1325—singling out O’Rourke by name as a holdout.

“I just think it’s a mistake, Beto, I think it’s a mistake, and if you truly want to change the system, then we gotta repeal that section,” the former Housing and Urban Development secretary said. “If not, then it might as well be the same policy.”

O’Rourke pivoted again to the issue of protecting asylum seekers, which Castro called a misdirection.

“A lot of folks that are coming are not seeking asylum—a lot of them are undocumented immigrants,” Castro said, adding that O’Rourke’s human trafficking concerns were already covered by other sections of the INA.

“I think you should do your homework on this issue,” Castro said. “If you did your homework on this issue, you would know that we should repeal this section.”

The exchange—easily the sharpest of the debate at that point—appeared to come out in Castro’s favor. According to Google Trends, searches for Castro spiked by more than 2,400 percent following his jostling with O’Rourke, whose campaign has been criticized for a dearth of the kind of policy specifics that may have helped Castro, previously polling at around 1 percent nationally, break out.

The Castro campaign clearly saw the exchange as a potential “moment,” if the former secretary’s remarks to reporters in the post-debate spin room were any indication.

“I find it very ironic that a senator from Massachusetts and a senator from New Jersey are the ones who understand this border policy and this law better than Congressman O’Rourke,” Castro said.