WASHINGTON — Democratic presidential candidates Julián Castro and Sen. Cory Booker, D-N.J., argued Sunday the President Trump’s rhetoric on immigration has helped to stoke racial resentment and a climate of hate in light of Saturday’s mass shooting in El Paso, Texas.

“We have a president of the United States who is particularly responsible," Booker said in an interview with "Meet the Press."

"In my faith, you have this idea that you reap what you sow, and he is sowing seeds of hatred in this country, this harvest of hate violence that we are seeing right now lies at his feet,” Booker said. “There is a complicity in the president's hatred that undermines the goodness and decency of Americans."

Speaking from his home state of Texas, Castro pointed to the anti-immigrant and anti-government manifesto that senior law enforcement officials tell NBC News they believe was written by the El Paso shooter.

Castro told "Meet the Press" that he sees a link between that rhetoric and the president’s comments about immigrants, which he said has helped contribute to the “toxic brew of white nationalism” in America.

“When he didn’t step up right away and condemn the neo-Nazis after Charlottesville, allowing that crowd for 13 seconds to chant ‘send her back’ a couple of weekends ago, he doesn’t have any credibility anymore,” Castro said.

“Like all Americans, I still hope that this president will do what most presidents have done throughout our history, which is to realize we have to do everything we can to try and unite Americans instead of fanning the flames of bigotry.”

Trump has repeatedly defended his tweet about sending four black Democratic congresswomen "home," denying it had any racist intent. And when confronted with why he stopped speaking at the rally as his supporters chanted “send her back,” Trump claimed he moved quickly to cut off the chants and that “I disagree with it.”

Late Saturday night, Trump tweeted “I know that I stand with everyone in this Country to condemn today’s hateful act.” On Sunday morning, after news of another mass shooting in Dayton, Ohio overnight, the president tweeted: “God bless the people of El Paso Texas. God bless the people of Dayton, Ohio.”

On Sunday, White House chief of staff Mick Mulvaney told "Meet the Press" that the president is "saddened and angry" by the shootings. He said Trump's first phone call after the El Paso shooting was to Attorney General Bill Barr in order to "find out how we can stop this stuff from happening."

Arguing that he understands that "some people don't approve of the verbiage the president uses," Mulvaney said that blaming Trump's rhetoric for the shootings is "disappointing."

"These are crazy people, sick people, and until we figure out why we are creating people like this in this culture, why we are giving them such wide audiences on Twitter, why we are making weapons available to them when they probably shouldn’t get them. Let’s talk about background checks, something we’ve worked on in this administration," Mulvaney said.

"Those are the conversations to have, not giving Cory Booker a chance to run for president this morning by blaming Donald Trump."

Twenty people were killed in Saturday’s shooting in an El Paso Walmart and a nearby shopping center, and 26 more are injured, law enforcement officials say.

El Paso Police Chief Gregory K. Allen told reporters on Saturday evening that the shooting seems to have “a nexus at this point to a hate crime.” The investigation is still ongoing.

Multiple senior law enforcement officials told NBC News that they believe the alleged shooter, identified as Petrick Wood Crusius of Texas, posted a screed on an extremist website shortly before the shooting. That message nods at the recent shooting in a New Zealand mosque, criticizes immigrants and government, both Republicans and Democrats. Crusius is currently in custody.

Less than 24 hours later, a shooting in Dayton, Ohio left 9 people dead and at least 26 more injured. The suspected shooter in that episode is dead.

Rep. Veronica Escobar, the Texas Democrat who represents El Paso, told “Meet the Press” Sunday that federal lawmakers have to “speak the truth” in light of these mass shootings.

“The truth is we have not just a gun epidemic in this country, but we have a hate epidemic in this country,” she said.

Both Booker and Castro urged Congress to address gun violence with new legislation on gun control.

Castro went on to argue for “common-sense gun reform,” specifically a ban on semi-automatic weapons as well as universal background checks and an expansion of “red-flag laws,” which allow law enforcement or family members to ask a court to temporarily take a firearm away from someone whom they believe could commit harm.

“This happened in Texas, one of the states with the highest rates of gun ownership — it has concealed carry, it has open carry. The shooter knew that he’d be walking into a store where a lot of people would be carrying a gun. That did not deter him,” Castro said.”

Dayton Democratic Mayor Nan Whaley also called on Congress to take steps to address gun violence in the wake of a deadly 24 hours.

“How many cities have to go through mass shootings before somebody has to change the law?” she asked.