Immigration became a focal point of the 2020 Democratic primary for the first time when candidates were forced to respond at Wednesday night’s debate to the horrific photo of a father and daughter who drowned attempting to cross the Rio Grande and seek asylum in the U.S.

Though Julián Castro had released a sweeping immigration proposal early in his campaign, most Democratic contenders, particularly those leading in polls, remained relatively mute on specifics.

The first debate night changed that. Castro sought to create a litmus test around one element of immigration law that criminalizes border crossings, which has received fresh scrutiny after President Donald Trump’s “zero tolerance” policy of separating families last year. Prior to the debate.l A day later, Sen. Cory Booker (D-N.J.), who also supports Castro’s proposal, announced a bill that would remove marijuana from the list of deportable offenses.

And several presidential contenders visited a for-profit detention center in Homestead, Florida during their time in the state to draw attention to conditions for migrants detained there.

The discussion continued Thursday as former Vice President Joe Biden, Sen. Bernie Sanders, Sen. Kamala Harris, South Bend, Ind., Mayor Pete Buttigieg and six more candidates debated the best path for addressing the crisis at the border during night two of the Democratic debate on NBC. Seven out of the 10 candidates on stage during the second night responded to Castro’s call, and raised their hand in support of decriminalization of border crossings, including Harris, Sanders and Buttigieg. Biden did not support the proposal.

Democratic operatives, mobilizers and immigrant-rights advocates said in interviews Thursday that the first debate helped jump-start a conversation about how Democrats plan to tackle immigration and counter Trump’s anti-immigrant rhetoric.

“Castro elevated the conversation to a place that we haven’t seen,” said Sayu Bhojwani, founder of New American Leaders, an organization that helps immigrants run for elected office.

The Texan called on Democrats running for president to support the repeal of Section 1325, a federal statute that makes illegal entry — or entry at a non-established port — a federal crime. Castro confronted one rival in particular, fellow Texan Beto O’Rourke.

“The fact that Secretary Castro put this out there and led the field on this really was an earthquake and until recently it was not getting treated like that,” said Maya Rupert, Castro’s campaign manager. “This has the potential to remake the way we were talking about how we can reform the immigration system.”

That law, Castro argued during the debate, allows Trump to prosecute families and separate children from their parents.

There’s a distinct but slight difference between Castro and O’Rourke’s proposals. Under Castro’s plan, wherever a migrant crosses — including the stretches of border with no entry points — they would be processed civilly not criminally. O’Rourke’s plan would repeal only the part of the law that applies to asylum seekers who are crossing between ports of entry. That means a migrant claiming asylum anywhere along the border would be processed civilly, but those who aren’t claiming asylum would continue to be charged criminally.

If Castro’s proposal were adopted and the entire 1325 immigration code repealed, it does not mean the respective agencies in charge of border security would have no enforcement mechanism to charge migrants. There are other measures under the law that border officers can use to charge migrants crossing the border and refer an offender to the Justice Department for criminal prosecution.

Republicans were quick to seize on the proposal to decriminalize border crossings. Trump’s campaign manager, Brad Parscale, accused Democrats of being “for OPEN BORDERS!”

“These debates are great, the American people can now see how far left the candidates are,” Parscale wrote. “If these policies were implemented millions of foreigners would flood our system and overwhelm public services. They are disconnected from reality!”

In an appearance on The View, Meghan McCain, the daughter of the late-John McCain, asked Castro how he would win over voters like her who oppose “open borders.”

“How can we possibly say that we have open borders when we have 654 miles of fencing, we have thousands of personnel at the border, we have planes, we have boats, we have helicopters, we have guns, we have security cameras,” said Castro. “We can maintain a secure border and people are still subject to the law, but what I don’t believe we should do is criminalize desperation.”

Marshall Fitz, managing director of the Emerson Immigration Collective, said Section 1325 gave the Trump administration authority to separate families when it launched its “zero tolerance” policy last year. But Fitz said repealing the law would not open up the country’s borders and noted there are multiple other provisions on the books that give border officials power to criminally charge migrants crossing outside of ports of entry.

Still, Fitz said he’s told campaigns not to dwell on decriminalizing border crossings, warning it exposes Democrats to attacks. “It’s just opening them up to this narrative of ‘Democrats are for open borders,’ which even under Castro’s proposal, they’re not,” Fitz said.

Instead, he said, Democrats should talk about how they would streamline the processing of migrants at the border. Currently there is a backlog of nearly 900,000 cases. Pending cases have increased by nearly 50 percent since Trump took office in 2017.

“Conventional Demoocratic wisdom is you can’t talk about immigration,” said Jess Morales Rocketto, former digital organizing director for Hillary Clinton.

But Rocketto Morales pushed back on the notion that embracing decriminalization of border crossings could cost the eventual Democratic nominee in the general election against Trump.

“That is absolutely the right message for Democratic primary voters,” said Morales Rocketto , executive director of Care in Action. “We could say the same exact thing as Republicans and they would still try to say we were for open borders. Republicans are going to try to make immigration a wedge issue because that is the entire Trump campaign strategy.”

In the month leading up to the debate, dozens of Democratic organizers and strategists working to energize new voters in key states like Nevada, Florida, Arizona and Texas, expressed frustration to POLITICO over the 2020 Democratic candidates’ silence on immigration. With the exception of Castro, many of them argued, Democrats were ceding ground to Trump, who plans to make immigration a central pillar of his campaign, like he did in 2016.

“The continuing horrors of what’s going on on the border, is pushing a vigorous conversation that I don’t think we could have had four years ago,” said Andrea Mercado, executive director of New Florida Majority, a progressive group that is registering black and Latino voters.

The photo of Oscar Ramirez and his almost two-year-old daughter drowned in the river, Mercado added, will “be seared in public imagination throughout this presidential cycle.”