Now his supporters expect action. “If he doesn’t pass that tariff, I will vote the other way next time,” warned Nicole Hargrove, who has worked at Carrier for a decade and a half and is not certain what she will do if and when her job goes to Mexico…

For Mr. Trump, now comes the hard part. In interviews in recent days and in March, Trump voters here made clear that if he does not follow through on his promises, they are prepared to turn on him, just as they are seemingly punishing Democrats today for not delivering the hope and change voters sought from President Obama after he won as an outsider in 2008.

And while Mr. Roell is a conservative, Mr. Trump’s tough talk about Carrier, the economy and the future of American manufacturing jobs also appealed to moderates like Darrell Presley, a steelworker in rural Crawfordsville, Ind., who voted for Mr. Obama in 2008. “He was for change, and said he would take care of the middle class, but he didn’t live up to those expectations,” Mr. Presley said. “I feel like the American people are at the point where they’ve had it, and this was the last chance.”…

As president, however, Mr. Trump will face a tough balance. Tariffs and trade wars stand to hurt American workers who make products that are exported to Mexico or China. Few voters will be happy paying more for imported goods.