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WASHINGTON — Newly released emails show that Environmental Protection Agency scientists raised strong objections to a 2018 decision by Scott Pruitt, who was head of the agency at the time, to exempt most of southeastern Wisconsin from federal limits on smog.

The decision by Mr. Pruitt was notable because it came as Gov. Scott Walker, a Republican, was campaigning for a third term and trying to bring a Foxconn factory, and thousands of new manufacturing jobs, to a part of the state where pollution levels already exceeded federal limits.

Mr. Walker ultimately lost his re-election bid to Tony Evers, a Democrat. And Foxconn , the Taiwanese consumer electronics giant, announced in January that it was reconsidering its plan to build a $10 billion plant in Wisconsin, though the company later said it would build a smaller factory in the state.

But, in spring 2018, as the governor’s race was heating up, Mr. Walker championed the Foxconn deal and the 13,000 jobs it promised to create. The factory, however, also threatened to create a new source of pollution in the region.