MSNBC host Mika Brzezinski said Monday that President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE once privately told her that the so-called "birther" theory he helped perpetuate about former President Obama was a harmful, yet effective message.

"We confronted him about 'birtherism,'" Brzezinski said on "Morning Joe," referring to the theory that Obama's birth certificate may be illegitimate. "We said its bad, it’s wrong. And he said in a low voice, 'I know it’s bad, but it works.'"

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"Racism in his mind works. That’s what he told us," she added.

Her comments came as a panel discussed Trump's rhetoric about immigration in the lead-up to the midterm elections. As Trump tours the nation to gin up support for Republican candidates, he's increasingly made the issue a focal part of his speeches.

The president has continued to voice outrage over the group of Central American migrants traveling to the U.S.-Mexico border, going so far as to label it an "invasion."

He also released an ad last week that showed Luis Bracamontes, a deported Mexican immigrant who returned to the U.S., bragging in court about killing police officers.

The ad features a narrator asking, "Who else would Democrats let in?"

Speaker Paul Ryan Paul Davis RyanKenosha will be a good bellwether in 2020 At indoor rally, Pence says election runs through Wisconsin Juan Williams: Breaking down the debates MORE (R-Wis.) called Trump on Sunday to ask him to focus on the economy in the final hours before Election Day, according to Politico.

But Trump reportedly bragged that his focus on issues related to immigration had electrified his base.

Trump acknowledged in September 2016 that Obama was born in the U.S. But The New York Times reported in 2017 that Trump continues to question the authenticity of the former president's birth certificate.

The Hill has reached out to the White House regarding Brzezinski's comments.