“I think everybody in Washington needs a kick in the rear,” Ms. Meadows, 68, said on Thursday as she ate fried fish at a diner in Warren, a weathered city at the county’s southern end. “And I think Washington needs to be done with the Clintons.”  She added, however, that she hoped Mr. Trump would not “do away with the health care” — Mr. Obama’s Affordable Care Act — as he had promised on the campaign trail. Her daughter had obtained subsidized insurance coverage through the law for $50 a month.  “I think he was bluffing,” Ms. Meadows said with a frown.  Mayor James R. Fouts of Warren said Trump supporters here were especially motivated by Mr. Trump’s promise to overturn or overhaul the North American Free Trade Agreement, which they blame for the loss of American manufacturing jobs to Mexico. All year, Mr. Trump has attacked Ford Motor Company in particular for planning to move all of its small car production to Mexico.  Noting that Senator Bernie Sanders of Vermont also criticized free trade agreements when he ran against Mrs. Clinton in the Democratic primary race, Mr. Fouts said that some who normally vote Democrat in Macomb County had initially supported Mr. Sanders and migrated to Mr. Trump only after Mrs. Clinton became the Democratic nominee.  “There were a significant number of Sanders people who made the transition to Trump,” said Mr. Fouts, whose office is nonpartisan. “Bernie might have won here; Joe Biden might have won. But Hillary was never going to be the candidate to convince people around here that she was going to make a difference in their lives.”  Mr. Fouts voted for Mr. Obama twice. But this time he rejected both Mrs. Clinton and Mr. Trump for a third-party candidate — which one, he would not say.  The last time the county backed a Republican presidential candidate was in 2004.  Mr. Trump may also have energized a segment of Macomb County voters who had not bothered to participate in the 2012 election. Voter turnout in the county was 4 percent higher this year, according to preliminary results, with 67 percent of registered voters casting ballots. On the other hand, some of the state’s most heavily Democratic counties, including Wayne, home to Detroit, and Genesee, home to Flint, saw less turnout than four years ago.  Amanda Rogers, a bartender in Warren, sat out the 2012 election but hustled to the polls to vote for Mr. Trump. Her boyfriend and her brother voted for the first time in their lives, she said. Ms. Rogers, 34, was motivated in part by what she saw as Mrs. Clinton’s lenient stance on immigration.  “We are drowning right now,” she said. “Our vets are homeless. There’s one out of every five American children starving right now. And Clinton wants to open the floodgates and let everybody else in.”  Ms. Rogers, who said she had “loved Bill Clinton as a president” and found Mr. Obama “all right,” added: “There’s people who’ve been here 12 years who don’t even care to learn the language but want to reap all the benefits of this country: food stamps, free health care, Section 8 housing, welfare checks. People are sick of that, especially in Macomb County.”  Muslims from places like Yemen and Bangladesh are the most visible immigrants here. Just south of Macomb County is Hamtramck, which in one generation went from overwhelmingly Polish Catholic to majority Muslim. In Macomb, the City of Sterling Heights, home to a large Ford plant, is facing a federal lawsuit after rejecting a proposed mosque last year.  Mr. Trump held a rally last Sunday in Sterling Heights, where he elicited boos against Mrs. Clinton when he said she wanted “virtually unlimited immigration from the most dangerous regions of the world,” and would “import generations of terrorism, extremism and radicalism into your schools and your communities.”  Macomb County, though still largely white, is becoming more diverse: 82.3 percent of its 865,000 residents were white in 2015, according to the Census Bureau, down from 85.4 percent in 2010. The black population grew to 11.4 percent, from 8.6 percent. About 10 percent of the population is foreign born.  Many here also complain that poverty and crime are growing. As Macomb helped assure Mr. Trump’s victory on Election Day, it also played a major role in the defeat of a local ballot initiative that would have taxed its residents, and those of four neighboring counties, to build a public transportation system connecting Detroit and its suburbs.  Jason Powrozek, 18, a high school senior from New Baltimore, on the more affluent north side of the county, said he had voted against the transportation measure because “I just felt it would speed up the transport of drugs up here from the inner city.” A first-time voter, he had volunteered for at the county Republican headquarters and went to New York for the Trump campaign’s election night party.  “He tells it like it is,” Jason said of Mr. Trump. “He speaks what people don’t want to say because it’s politically incorrect.”  Mr. Trump also spoke on Halloween at Macomb Community College.  Frank Pitcher, 49, who lives in Sterling Heights and has worked at its Ford plant for 23 years, went to the Trump rally there and said he was surprised at how many of his co-workers he saw.  “I took some pictures with people there and posted on my Facebook because I wasn’t going to hide how I was voting,” he said. “I’m not ashamed of where I stand.”  A version of this article appears in print on November 13, 2016, on page A14 of the New York edition. Order Reprints| Today's Paper|Subscribe
In Macomb County, where the term “Reagan Democrats” was coined, voters found in Mr. Trump a candidate who understood the importance of trade and manufacturing.