Donald Trump made an enemy of Ohio Gov. John Kasich during the Republican primary, and in the months since, Kasich and many of his staff have refused to work with Trump's campaign, which could lose the key state for the billionaire GOP candidate.

"You're a family, and if somebody attacks your family and says awful things about your family, are you inclined to help that person?" Michael Hartley, a Columbus-based Republican consultant, told The New York Times, referring to Trump.

"The answer is no. To be honest, the Trump people did this to themselves."

Kasich, a two-term governor and former congressman from the Buckeye State, has Ohio's best political ground team, powering him to a win with almost two-thirds of the vote in his 2014 re-election bid. Getting out the vote is key to winning Ohio, but few Kasich supporters are willing to work with Trump.

"Kasich had the best ground game for the last eight years in Ohio," Hartley continued. "If you want to win Ohio, you need the Kasich team."

Kasich did not forbid his campaign staff from working for Trump, but most have refused to do so out of loyalty to the governor. No Republican presidential candidate has won election without winning in Ohio since Abraham Lincoln in 1860, according to The Columbus Dispatch.

Some, like Ohio GOP chairman Matt Borges, have reluctantly decided to support Trump, despite previously opposing the real estate mogul.

"You play the hand you're dealt and go out and do the best you can," Borges told the Times. "We will have an effort that's parallel to any other presidential effort we've had in Ohio."

The trump campaign announced recently that they were opening 15 field offices throughout the state, and with the Ohio and national Republican parties, hired 70 organizers with 40 more to come before the election.

Hillary Clinton's campaign, by contrast, had 180 organizers in the state as of August, and over 35 field offices.

"What is going to be damaging to the Donald Trump campaign," Betty Montgomery, Ohio's former Republican attorney general, told the Times, "is the equivocation on the part of regular Republicans, those die-hard Republicans who show up at conventions and work the polls."

On Monday, Trump told ABC News that he was "disappointed" in Kasich for backing out of the pledge the Republican candidates made last year to support the party nominee.

"I hold Gov. Kasich in high regard. Look, these two went through a tough competition together," Trump's running mate, Indiana Gov. Mike Pence, said of Trump and Kasich. "I respect that, these things sometimes take time."