Democrats are trying to make progress with voters when it comes to immigration and border security.

A recent ABC News poll found Donald Trump retains the upper hand on the issue, keeping the race a closely contested one.

Trump leads Harris by 10 points in trust to handle the immigration situation at the U.S.-Mexico border, though he had led by 14 points in July.

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Texas sheriff: Trump 'made our jobs harder'

Bexar County Sheriff Javier Salazar spoke at the DNC about Trump, encouraging congressional Republicans to kill the bipartisan border deal negotiated earlier this year.

At the DNC, speakers are bashing Trump for encouraging congressional Republicans to kill the bipartisan border deal negotiated earlier this year.

"He is a self-serving man," Javier Salazar, the sheriff of Bexar County, Texas, just said on stage. "Just like when he killed the border bill, he just made our jobs harder."

Olivia Troye, a former Trump White House National Security official, is on stage -- one of several Republicans scheduled to speak during the DNC this week.

In 2020, the New Jersey senator mounted a campaign for the Democratic nomination after decades on the rise within the party.

The theme of his campaign was unity and love. His optimistic messaging was on display again tonight as he spoke.

"We're not going to lose our faith," he said. "Look, I want everybody in here to let us all say it together: I believe in America."

The crowd repeated the phrase back to him.

As the programming shifts to border security, Texas Rep. Veronica Escobar said that former President Donald Trump and his imitators see the border as a "political opportunity to exploit instead of an issue to address."

"They are not serious people. You know who is serious? Kamala Harris," she said, talking about Harris' visit to El Paso engaging with stakeholders.

"She recognized that the situation at the border is complicated -- as filled with challenges as it is with opportunities," Escobar said.