Ohio Gov. John Kasich, the Republican presidential candidate who lasted the longest against Donald Trump during the GOP primary season, won’t give the billionaire businessman his endorsement, yet. Speaking to MSNBC in an interview aired Thursday, Kasich apologized for the outcome of the party’s nominating race and called it “painful,” Politico reported.

“We’ll see where it ends up,” Kasich said, specifically mentioning he disagreed with Trump’s comments about banning Muslim immigration. “I’m not making any final decision yet, but at this point, I just can’t do it.”

It wasn’t the first time Kasich, who secured 161 of the 1,237 delegates necessary to win the Republican presidential nomination, has indicated he’s not behind Trump. The governor has increasingly been speaking out against the presumptive GOP nominee since he dropped out of the race May 4.

Kasich told the Plain Dealer in Cleveland last month he was not going to vote for presumptive Democratic nominee Hillary Clinton, and that he didn’t support Trump, either. “Unless I see a fundamental change, it’s really hard for me to do a merger,” Kasich said. “If the values are not somewhat similar — if the culture is not somewhat similar — it’s hard to do a merger. ... If he changes, that’s a whole new ballgame.”

Kasich also openly criticized Trump for suggesting U.S. District Judge Gonzalo P. Curiel couldn’t fairly oversee a case involving the now-defunct Trump University because of Curiel’s Mexican heritage. Kasich called Trump’s gaffe “just terrible,” USA Today reported.

GettyImages-483203188 Billionaire businessman Donald Trump (right) confers with Ohio Gov. John Kasich during a break in a Republican presidential debate at the Quicken Loans Arena in Cleveland Aug. 6, 2015. Photo: Getty Images

Kasich’s name has been floating for weeks as a potential vice presidential pick for Trump. But the governor himself has attempted to tamp down any rumors of a partnership. “There was never a chance of that,” Kasich told Fox News recently. “Never, not even a consideration. We’re too different.”

Kasich isn’t alone: A number of party leaders have come out to declare they will not support Trump at the Republican National Convention in Cleveland July 18-21. They include Maryland Gov. Larry Hogan, Massachusetts Gov. Charlie Baker, U.S. Sen. Ben Sasse of Nebraska and 2012 GOP presidential nominee Mitt Romney, according to the Daily Wire.