President-elect Donald Trump pledged to be "so presidential you will be bored" during the election, but he continues to keep Americans on their toes after again taking to Twitter to battle his most recent critic.

Chuck Jones, president of United Steelworkers 1999, told NBC News that he had been harassed and threatened in the wake of Trump's latest attack — a broadside against Jones leadership of union workers at a Carrier manufacturing plant in Indiana that took center stage last week.

Jones has not been shy about telling publications that Trump broke his promise to save jobs at the Carrier plant, a pledge on which the president-elect campaigned.

Trump recently proclaimed that he helped save about 1,100 jobs at the plant that were slated to be moved to Mexico, which is untrue. Instead, the deal saves closer to 800 positions, according to Jones. Carrier’s parent company gets $7 million in tax cuts and incentives over 10 years.

Jones said Trump tried to take credit for 350 research and development jobs that were already planned to remain in Indiana.

Trump did not address the reasons for the feud directly, but instead stated via a tweet that Jones had done a "terrible job" and suggested that he was the reason companies were leaving the country.

Chuck Jones, who is President of United Steelworkers 1999, has done a terrible job representing workers. No wonder companies flee country! — Donald J. Trump (@realDonaldTrump) December 8, 2016

The national union responded not long after, calling Jones a "hero" who'd tried to save all of the imperiled jobs.

Chuck is a hero not a scapegoat: you, others know about Carrier because of his, members' tireless work since day 1 to save ALL jobs there. https://t.co/C9fvwajHY7 — United Steelworkers (@steelworkers) December 8, 2016

More than an hour later, Trump returned to Twitter to say the lost jobs were the fault of the local union. Trump said the union should "spend more time working-less time talking. Reduce dues."

If United Steelworkers 1999 was any good, they would have kept those jobs in Indiana. Spend more time working-less time talking. Reduce dues — Donald J. Trump (@realDonaldTrump) December 8, 2016

The union replied that members' dues were used to save jobs.

Dues have helped us file 45+ cases against bad trade; saving jobs in tire, paper, steel, etc. We walk the walk. #imwithchuck #wearewithchuck https://t.co/PlGznkwrTS — United Steelworkers (@steelworkers) December 8, 2016

The argument started 20 minutes after Jones appeared on CNN and said 550 jobs were still heading for Mexico from Carrier's Indianapolis facility, while 700 jobs from its Huntington facility would also be sent to Mexico.

Jones later told NBC News: "I tried to correct some of his math, and he took exception to it."

"For him to say I'm a horrible labor leader, I take it as a positive, because that must mean that we're doing something so people can earn a decent living wage-wise and benefit-wise," Jones added.

Jones said some of Trump's passionate Twitter followers are now harassing him.

"I'm getting threats and everything else from some of his supporters," Jones said. "I'm getting them all day long — now they're kicked up a notch."

Nobody should be allowed to burn the American flag - if they do, there must be consequences - perhaps loss of citizenship or year in jail! — Donald J. Trump (@realDonaldTrump) November 29, 2016

Since winning the election, Trump has used the social media platform to criticize China, Boeing, the cast of "Hamilton," the news media in general, the Green Party and its presidential nominee, Jill Stein, "Saturday Night Live," Cuba, protesters and more.

He also tweeted that cases of voter fraud caused him to lose the popular vote, a claim for which there is no evidence.

In addition to winning the Electoral College in a landslide, I won the popular vote if you deduct the millions of people who voted illegally — Donald J. Trump (@realDonaldTrump) November 27, 2016

On Twitter, Trump also took credit for saving a Ford plant that was never slated to close.

I worked hard with Bill Ford to keep the Lincoln plant in Kentucky. I owed it to the great State of Kentucky for their confidence in me! — Donald J. Trump (@realDonaldTrump) November 18, 2016

The president-elect's transition team has not apologized or produced any corrections.