And now that the contest has landed in Indiana -- with a potentially fateful primary coming Tuesday -- the focus on the Carrier story has reached a fever pitch.
Donald Trump has made Carrier's move a central part of his speeches about trade, hitting on the nexus of lost jobs and the impact of NAFTA and trade deficits, in particular.
Speaking at his victory speech following the "Acela primary" victories, Trump touted his support on the issue long before others were focusing on it.
"I think we're going to do great in Indiana. Indiana is the home of Carrier which is leaving the state, I've been talking about it for four months, long before we knew Indiana would be so important," he said last Tuesday.
But the flood of attention for the workers at the plant these past few weeks has been bittersweet at best -- unearthing feelings of ambivalence toward the White House contenders who say they will ride in to save their jobs and others, while they also relish watching Carrier become the target of 2016's raw, populist anger.
Among a handful of union members who gathered at the United Steelworkers office building on the outskirts of downtown Sunday, there was a sense that none of the candidates truly understand what they are going through.
"I see it now as some of the candidates being opportunists, they're taking advantage of a situation, they're exploiting it," said Robert James, 57, of Indianapolis, a forklift operator at the plant. "But they're also being helpful to a degree. Carrier deserves a bigger spotlight for what they done and they asked for this, it's not a steelworker fight. Carrier made it, so they propelled themselves out there and -- (he then paused, and smiled) -- I think the candidates are doing a great job."
James said when he first heard that the plant was moving 1,400 jobs to Monterrey, Mexico, he thought it was a joke. So he went back to sleep (he works a night shift.) But his phone wouldn't stop ringing.
"I still don't believe it really. You know what I'm saying? It's just kind of hard to swallow," he said.
The plant is phasing out the jobs over the next three years, sending the jobs to the new plant in Monterrey, Mexico.
Appeals to workers like James have been a centerpiece of speeches from Trump, Ted Cruz, Hillary Clinton and Bernie Sanders here in Indiana, which is filled with blue-collar workers who either have or lost manufacturing jobs.
Sanders, who has been endorsed by United Steelworkers Local 1999, marched with workers here in Indianapolis last Friday. "Today we are sending a very loud and clear message to the CEO of United Technologies -- stop the greed, stop destroying the middle class in America, respect your workers, respect the American people!"
Trade issues and manufacturing jobs are critical to winning Indiana -- a Rust Belt state that is typically more conservative than places like Wisconsin and Michigan. And it's also where Cruz is making what could be his last stand.
Cruz, who has been a staunch supporter of free trade agreements, made a populist pitch here, saying that he would bring Carrier jobs back by rewriting government regulations.
"In a few years, you know what's going to happen? We're going to see Carrier bringing those jobs back to America," Cruz said last week at a joint press conference with his newly-minted running mate, Carly Fiorina. "Not because some government bully like Barack Obama or like Donald Trump or Hillary Clinton used government power to say 'No, you must do business even when have taxes and regulations that are killing your business.'"
But Trump said he would not let Cruz wrestle the title of Carrier champion from him.
"I'm the one that brings up Carrier all the time! Then all the sudden this morning I hear Cruz, he said, 'And Carrier air conditioning.' I've been talking about this company for four months, all of the sudden he starts talking about Carrier," Trump said last Thursday during a stop in Indiana. "Carrier's my baby. I want to do the number on Carrier."
A Carrier spokeswoman did not answer questions about the 2016 campaign, and the company emphasized it is trying to help workers find new jobs -- including support for retraining.
"Our aim is to provide our employees with both time and opportunity for a smooth transition," said Carrier spokeswoman Michelle Caldwell. "We appreciate the contributions our employees make every day and seek to provide best-in-class support for continuing education now and for up to four years in any career path of their choosing."
The union membership is hardly unified as a bloc behind any one candidate, said United Steelworkers Local 1999 President Chuck Jones.
"Our local endorsed Bernie Sanders for President. But without a doubt we got a little bit of Trump, Kasich, Hillary, a little bit of everybody," he said.
There is still a deep mistrust of Clinton on the trade issue. Jones specifically blamed Clinton and NAFTA -- which opened trade between Mexico and the U.S. -- for the loss of their jobs.
"I know that even though she says she is against some of the trade bills, Hillary Clinton was the first lady when her husband Bill Clinton was president. She endorsed NAFTA," Jones said.
Frank Staples, 37, and an 11-year veteran of Carrier, said none of the candidates have come close, because undoing those trade measures would require winning Congress -- not just the White House.
"You can't really take the politics serious in this, the presidential candidates are saying what the people want to hear," Staples said.
Staples is supporting Sanders, but acknowledged that Trump is singing a siren song for his colleagues who are not as well versed in the politics and policy of trade.
"I see through a lot of that stuff," he said. "But there are a lot of people that are just blind to it, they just like the fact that he's talking about Carrier and what they're doing."