CNN  — 

Julián Castro walked onto the debate stage in Miami on Wednesday night as a longshot candidate with a fat resume but stubbornly low poll numbers.

Two hours later, as the cameras dimmed on the first Democratic debate of the 2020 presidential election, the former Housing and Urban Development secretary was a Twitter trend of his own after delivering an emotional response to the immigrant crisis on the US-Mexico border and using his policy chops to sharply attack the better-known Texan in the race, former Rep. Beto O’Rourke. He also had his best night of fundraising on Wednesday and overnight into Thursday, his campaign spokesman told CNN, further proof that his debate performance gave him a boost.

The former San Antonio, Texas, mayor and the grandson of a Mexican immigrant drew cheers when he called for the passage of the Equal Rights Amendment. He flashed anger at the Trump administration’s immigration policies, calling the drowning deaths this week in the Rio Grande of Oscar Alberto Martinez and his 23-month-old daughter, Valeria, “heartbreaking” but also a tragedy “that should piss us all off.”

“Well, clearly I had a great night,” Castro said on Thursday to CNN’s John Berman on “New Day.”

“Last night, people saw that I have strong track record of getting things done. I have the right experience. I have a strong vision for the future of the country. And as you played the clip there, people want to know can you stand up to Donald Trump? Can you handle yourself? Can you hold your own? And I more than held my own last night.”

His biggest breakout of the night came as he jousted with O’Rourke on the question of whether crossing the border from Mexico should be a crime.

Castro has touted an immigration plan that would decriminalize crossing the border by doing away with a provision, known as Section 1325, of the Immigration and Nationality Act that applies a criminal violation to anyone crossing the border illegally, as opposed to treating it as a civil infraction.

O’Rourke’s immigration plan calls for a “comprehensive re-write” of immigration laws, and he noted he has introduced legislation in Congress to decriminalize those seeking asylum.

Castro quickly interjected, arguing that O’Rourke’s proposal only helps asylum seekers but many people who are charged with crossing the border are undocumented immigrants.

“I think you should do your homework on this issue,” Castro told O’Rourke and challenged “all of the candidates” to support the provision’s repeal.

“The conversation that Congressman O’Rourke and I had was that he refuses to support (eliminating the provision), he told Berman on Thursday. “And if you want to guarantee that another administration in the future does not separate families as cruelly as Donald Trump has, then the best way to do that, the only way to do that, is to eliminate Section 1325.”

And after a debate featuring O’Rourke breaking into English-accented Spanish, Castro, the only Latino presidential candidate among two dozen contenders, saved his Spanish for his closing statement, saying among other things: “On Jan. 20, 2021, we’ll say adios to Donald Trump.”

Even before the debate ended, it was clear Castro was having a moment, with search interest on his name, surging 2,400% on Google. And an aide to Castro said the campaign saw a 4-digit percentage increase in total daily donations and in new daily donations after the debate.

Even fellow presidential candidate Sen. Elizabeth Warren texted Castro Wednesday night to tell him that he did a good job.

“He bought himself a lifeline tonight,” CNN contributor Van Jones said of Castro, minutes after the debate ended.

He’ll need it.

Castro has trailed his Democratic rivals in fundraising, collecting $1.1 million in primary and general election money in the first three months of the year – a fraction of the $18.2 million brought in by the fundraising leader of the first quarter, Vermont Sen. Bernie Sanders. So, it was no surprise that Castro on Twitter and in a post-debate appearance Wednesday on CNN immediately began asking for more political donations.

“A lot of people may not have been paying attention to my campaign before tonight,” Castro told CNN’s Anderson Cooper, “but they are now.”

CNN’s Dan Merica, Devan Cole and MJ Lee contributed to this report.