Voters from across party lines in Fox News' focus group reacted in real time to former President Trump's jab at Vice PresidentHarris for allegedly copying some of his platform policies.

"Everything that she believed three years ago and four years ago is out the window. She's going to my philosophy now," Trump said. 

"In fact, I was going to send her a ‘MAGA’ hat. She's going to my philosophy. But if she ever got elected, she will change it, and it will be the end of our country," he added. "She's a Marxist. Everybody knows she's a Marxist. Her father's a Marxist professor in economics, and he taught her well." 

Republican voters' approval shot up during Trump's remarks, while Independent support increased slightly, and Democrat voters' approval dipped, according to the Fox News dial. 

Harris was under fire from critics and conservatives last month for echoing former President Trump’s campaign vow to not tax service industry employees' tips after the Biden-Harris administration rolled out a plan to crack down on tips for people who work in the service industry.

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ABC News Hosts Presidential Debate Between Donald Trump And VP Kamala Harris At The National Constitution Center In Philadelphia

Former President Trump and Vice President Kamala Harris greet each other before their debate at the National Constitution Center on Sept. 10, 2024, in Philadelphia. (Win McNamee/Getty Images)

The copycat dig Tuesday night came after Harris had attacked Trump’s trade policies with China. 

"He invited trade wars. You want to talk about his deal with China. What he ended up doing is under Donald Trump's presidency, he ended up selling American chips to China to help them improve and modernize their military. Basically sold us out," Harris said. "When a policy about China should be in making sure the United States of America wins the competition for the 21st century."

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Harris ABC debate

Vice President Kamala Harris during the presidential debate at the National Constitution Center in Philadelphia on Tuesday, Sept. 10, 2024. (Doug Mills/The New York Times/Bloomberg via Getty Images)

Harris said that "means focusing on the details of what that requires, focusing on relationships with our allies, focusing on investing in American-based technology so that we win the race on AI, on quantum computing, focusing on what we need to do to support America's workforce so that we don't end up having – on the short end of the stick in terms of workers’ rights." 

"But what Donald Trump did, let's talk about this with COVID, is he actually thanked President Xi for what he did during COVID. Look at his tweet. ‘Thank you, President Xi, exclamation point,'" Harris added. "When we know that Xi was responsible for lacking and not giving us transparency about the origins of COVID." 

Debate split screen

Former President Trump and Vice President Kamala Harris during the debate. (Screenshot: Fox News simulcast of ABC News Presidential Debate)

"First of all, they bought the chips from Taiwan. We hardly make chips anymore because of philosophies like they have, and policies like they have. I don't say her because she has no policy," Trump responded. 

Former independent presidential candidate Robert F. Kennedy, Jr., who endorsed Trump weeks ago, chimed in on X about the exchange – but regarding what Harris said of COVID origins. 

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"VP Harris sounds like she just admitted the COVID virus originated in a lab. That was one of the ‘conspiracy theories’ the Biden-Harris administration censored on the Internet," Kennedy wrote. 

Fox News Digital's Emma Colton contributed to this report.