Just before the strike vote, Mr. Biden called Shawn Fain, the president of the U.A.W. as well as top executives of the car companies. Aides said that the president told the parties to ensure that workers get a fair contract and he urged both sides to stay at the negotiating table.
That did not happen. Economists say a lengthy strike, if it goes on for weeks or even months, could be a blow to the American economy, especially in the middle of the country.
How Mr. Biden navigates the situation could have a significant impact on his hopes for re-election. In a CNN poll earlier this month, just 39 percent of people approved of the job he is doing as president and 58 percent said his policies have made economic conditions in the United States worse, not better.
The fact that the strike is centered in Michigan is also critical. Mr. Biden won the state over former President Donald J. Trump with just over 50 percent of the vote. Without the state’s 16 electoral votes, Mr. Biden would not have defeated his rival.
Still, the president is unwavering on policies toward both unions and the environment. In a Labor Day speech in Philadelphia, Mr. Biden renewed both his vision about what he called a “transition to an electric vehicle future made in America” — which he said will protect jobs — and his rock-solid belief in unions.
“You know, there are a lot of politicians in this country who don’t know how to say the word ‘union,’” he said. “They talk about labor, but they don’t say ‘union.’ It’s ‘union.’ I’m one of the — I’m proud to say ‘union.’ I’m proud to be the most pro-union president.”