CLEVELAND — Donald Trump will leave Ohio after a week-long convention without the support of its Republican governor, an integral figure within a state that can determine who wins the presidency.

John Kasich has refused to support Trump or attend the convention in his home state, and instead engaged in counter programming around Cleveland that was decidedly non-Trumpian. At one of his many events within walking distance from the convention arena, he told an audience at a think tank on Tuesday that he was “very, very concerned” about the “stew of growing nationalism, growing isolationism, anti-immigration and anti-trade.”

The governor’s schedule and his refusal to welcome the Republican presidential candidate to his state irritated the Trump campaign and some party officials seeking unity. Trump Campaign Chairman Paul Manafort began the week by criticizing the governor, calling him “petulant” and an “embarrassment” to Ohio.

“It’s very sad that the host governor doesn’t have the decency to show — he doesn’t have to endorse Trump, but he could have come out of decency and said, ‘Welcome to Ohio. I’m glad you’re in Ohio,’” Newt Gingrich told RealClearPolitics. “I think it’s goofy for John to do this.”

The war of words and actions could be consequential to Republicans’ hope of winning the White House in November. Kasich is a twice-elected GOP governor with a vast political network that reaches multiple key constituencies. The comments from Manafort struck a nerve with the state party, on which the Trump campaign will depend to mobilize voters.

“We’re going to work hard for him to carry the state. But if he or his campaign keeps criticizing John Kasich, he’s going to lose. So that’s something that needs to stop,” Ohio Republican Party Chairman Matt Borges told RCP. “We’re the people who have been doing nothing but winning elections in this state for 25 years. He knows he needs to listen to people who know what they’re doing.”

The feud could create trouble for the Trump campaign’s hiring in Ohio. The Cincinnati Enquirer reported that one veteran Republican and close Kasich ally turned down an opportunity to join the campaign.

“Do endorsements matter? Not really. But does Donald Trump have a message right now that can win Ohio? No,” said Chris Schrimpf, Kasich’s communications director.

“The most important thing to Governor Kasich right now is making sure Rob Portman gets re-elected,” Schrimpf said, referring to the Republican senator engaged in one of the most competitive re-election contests this cycle. “It’s the rare instance where the Trump folks would be lucky that the Portman campaign is one of the best run in the country with one of the best ground games in the country, which they’ve set up on their own.”

After the Ohio governor left the race in May, the Trump and Kasich campaigns spoke about possible endorsements. (The New York Times reported that Trump’s son approached Kasich about being a running mate. The governor declined and wasn’t vetted.) Soon after, Kasich told Trump to read his “Two Paths” speech that he gave in New York in April that urged against politics of fear and division. Trump never responded, according to the Kasich team.

“They have two very different, competing views for the Republican Party in America,” Ohio Secretary of State John Husted told RCP of the governor and Trump. “We’re still having the competing discussion about what the future of the Republican Party should be. And frankly, I think if we can get to somewhere where John Kasich was — the hopeful, optimistic view of America … then the GOP will have a winning message. But right now we don’t have one.”

Polls show Ohio to be one of the most competitive battleground states this cycle. No Republican has won the presidency without Ohio. “Ohio is middle America, but Ohio really is the determiner of where this nation goes,” House Speaker Paul Ryan said this week at the Buckeye State delegation breakfast. “As Ohio goes, so goes America.”

The Trump campaign believes the candidate’s populist appeal could attract support beyond traditional Republicans. Hosting the convention in Cleveland was considered an effort by the party to win back Ohio, a state that has been elusive since the Bush years. The campaign hired Republican veteran Bob Paduchik, who ran George W. Bush’s Ohio operation, to head up the Trump efforts there.

“You win battleground states by addition, by building coalitions. The onus is on Mr. Trump and his campaign to win Ohio,” Kasich’s top strategist, John Weaver, told RCP. “I think the anti-Clinton message is important, but we’re just talking to each other. So, for the disaffected Republicans and Independents and disaffected Democrats, what’s the positive message about bringing people together?”

But the Ohio Republican Party remains resolute about its potential this November.

“Paul Manafort made a mistake this week. Everybody makes mistakes. Sometimes really stupid ones. But we will recover from this and lay our sabers down and move forward to win Ohio,” said Borges. “I think the message was delivered.”