Republican vice presidential candidate Sen. JD Vance, R-Ohio, on Thursday speculated that the reason Pennsylvania is trending red could be related to former President Trump's proposal on tariffs, warning that voters in the battleground shouldn't trust Vice President Kamala Harris' promise to revive American manufacturing.

"This is where President Trump gets the most criticism, but it's also where President Trump is the most right," Vance said at a campaign stop in Pittsburgh, referencing Trump's plan to implement tariffs as a way to discourage imports and drive domestic production. Harris has criticized the plan as risking price hikes. 

"If you are a business, and you rely on foreign slave labor at $3 a day, the only way to rebuild American manufacturing is to say, if you want to bring that product made by slave labor back into the United States of America, you're going to pay a big fat tariff before you get it back into our country," Vance said. 

"My message to Pennsylvanians: don't trust anybody, especially Kamala Harris, when she tells you she's going to rebuild American manufacturing without forcing the Chinese to pay a tariff," he continued, speaking to voters in the critical swing state. "There is no way to do it unless you're fighting hard against the people who are stealing our jobs and stealing our manufacturing industries, you got to do it. And if you're not doing it, you're not serious about rebuilding the American middle class." 

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Vance campaigns in Pittsburgh

Sen. JD Vance, R-Ohio, speaks at a campaign event at The Pennsylvanian in Pittsburgh on Thursday. (AP Photo/Rebecca Droke)

Vance was responding to a reporter’s question about what county in Pennsylvania the Trump campaign would turn to first to determine whether they won the election. 

"I'm not much of a political prognosticator. The only prognostication I'll make is that Pennsylvania is going to make Donald Trump the next President of the United States," Vance said. "I really do believe that." 

Vance overlooks Pittsburgh crowd

Sen. JD Vance, R-Ohio, speaks at a campaign event in Pittsburgh on Thursday.  (AP Photo/Rebecca Droke)

"If you look at the early voting numbers, if you look at how much redder Pennsylvania has gotten in just the last couple of years, we are going to win this race so long as we work for it over the next 19 days," Trump's running mate added. "I really do believe that." 

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Vance credited Pennsylvania's tradition of world-renowned steel manufacturing and craftsmanship, saying the country has unfortunately "gotten way too far away from self-reliance." 

Crowd of supporters see Vance in Pittsburgh

Supporters listen to Sen. JD Vance, R-Ohio, speak at a campaign event at The Pennsylvanian in Pittsburgh on Thursday. (AP Photo/Rebecca Droke)

The senator turned vice presidential pick said he believes Trump's message is resonating in Pennsylvania more than Republicans from 20 years ago had because of the 45th president's belief in "making things in America and stamping more products with the incredible label ‘Made in the USA.’" 

Citing a statistic he said "scares the hell out of me," Vance said China has 32% of world manufacturing GDP, meaning 32% of the goods made worldwide are made there, compared to just 18% made in the U.S.

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"That means China makes more stuff — I'm talking about the pharmaceuticals that we put into the bodies of our children, some of the important weapons systems of the future, the computer chips," he said. "We've got to make more of our own stuff in the United States of America. And the way to do that is to lower regulations, lower energy costs for American businesses, and to rebuild the great American middle class."