Julián Castro spars with Democratic front-runner Joe Biden during party's second presidential debate

DETROIT — Presidential candidate Julián Castro of San Antonio sharply criticized his party's frontrunner for the Democratic nomination, former Vice President Joe Biden, as the pair squared off Wednesday on immigration and decriminalizing improper crossings of the U.S. border.

Castro once again advocated for the repeal of Section 1325, a provision of the Immigration and Nationality Act that criminalizes such entry into the United States, after being asked how his stance is different from having open borders.

"If you elect me president, you're electing me not to follow. You're electing me to lead," Castro said. "And open borders is a right-wing talking point, and frankly, I'm disappointed that some folks on this stage have taken the bait."

Biden then took direct aim at Castro, the former Housing and Urban Development secretary with whom he served during the Obama administration.

"I found that Julián, excuse me, the secretary, we sat together in many meetings," Biden said. "I never heard him talk about any of this when he was the secretary."

"If you cross the border illegally, you should be able to be sent back," Biden added. "It's a crime. It's a crime."

It was the same issue on which Castro sparred with his fellow Texan, Beto O'Rourke, in last month's Democratic party debate. The stakes were high for Castro on Wednesday. He has yet to meet the polling threshold in order to qualify for the September Democratic debate.

Candidate after candidate on the stage took aim at Biden during Wednesday's portion of the party's second debate. But the Castro skirmish became one of the most direct and personal.

"Mr. Vice President, it looks like one of us has learned the lessons of the past. One of us hasn't," Castro said. The Texan then said that there still ought to be consequences if one crosses the border without authorization, but the penalties should be civil.

"What we need are politicians who have some guts on this issue," he added.

"I have guts enough to say his plan doesn't make sense," Biden retorted.

U.S. Rep. Joaquin Castro, a San Antonio Democrat and the candidate's brother, further explained after the debate that Obama administration was mistaken in "not getting rid of" Section 1325 when Democrats held power.

"Unless you repeal that section, a future president can treat people inhumanely and put parents and kids in cages," Joaquin Castro said. "And I know that the counter-argument ... is that you can just defer prosecution, for example ... but nobody on that stage ... is going to be president forever. The next Republican president, or even a Democratic president, if they wanted to, could do what Donald Trump is doing and that is unacceptable."

The former vice president; U.S. Sens. Michael Bennet of Colorado, Cory Booker of New Jersey, Kirsten Gillibrand of New York and Kamala Harris of California; Washington Gov. Jay Inslee; U.S. Rep. Tulsi Gabbard of Hawaii; entrepreneur Andrew Young; and New York City Mayor Bill de Blasio also participated in this round of debates. O'Rourke appeared in the first round of CNN debates Tuesday night.

Castro also addressed President Donald Trump's recent rash of tweets denigrating the city of Baltimore.

"The president is a racist, and this is just one more example of it," Castro said.

He added that he would invest in education and work to desegregate housing in order order to address the racial divide within the country.

Late in the debate, Castro re-iterated his support for the impeachment of Trump. And he pushed back on some Democratic fears that an impeachment might strengthen Trump, much like the 1998 Republican impeachment of President Bill Clinton strengthened his political standing.

"Too many folks in the Senate and in the Congress have been spooked by 1998," Castro said. "I believe that times are different. In fact, I think that folks are making a mistake by not pursuing impeachment."