How John Kasich May Lose To Donald Trump. Again.

Ohio governor and former Republican presidential primary challenger John Kasich was one of the last to hold out in the race against Donald Trump — and now, he's one of the only remaining prominent Republican lawmakers to hold out on endorsing his party's candidate. Kasich has not been able to bring himself to back Trump, despite pressure from his party. As Trump's poll numbers improve in Ohio, does this spell bad news for Kasich going forward?

Among voters in his state, Kasich is quite popular, though that wasn't always the case; his approval rating steadily rose from a mere 30 percent in 2011 to 62 percent in 2015, PolitiFact reported. But that number began to dip into the 50s in 2016. Public Policy Polling reported that his approval rating of 73 percent among Republican voters in March declined to 59 percent in July. Interestingly, his approval among Democrats increased from 36 to 43 percent. His principled refusal to speak in support of Trump is likely hurting him among his voter base, but endearing him to the other side of the aisle.

Most polls throughout the spring and summer showed Hillary Clinton leading in the swing state. But the situation reversed in September, as many of the state's Republican leaders rallied behind Trump and voters followed suit. A Bloomberg poll from mid-September found that 85 percent of Republican and right-leaning voters plan to vote for Trump; that number is up from 77 percent who said they would do so when Quinnipiac posed the question in July.

Whether Kasich's withholding of an endorsement will hurt him among Buckeye voters when he's up for re-election again will hinge on whether he picks up enough support among Democrats and left-leaning independents in the state to make up for those on the right he has lost. But it's clear that his admitted disdain for Trump is not making him the most popular guy in the party among fellow Republican officials.

Over the weekend, Republican National Committee Chairman Reince Priebus said to CBS on Sunday regarding primary challengers like Kasich, along with Sen. Ted Cruz: "Those people need to get on board. And if they're thinking they're going to run again someday, I think that we're going to evaluate the process — of the nomination process and I don't think it's going to be that easy for them." All Republican primary candidates signed an agreement that they would endorse the party's eventual nominee, whoever it was.

Trump's improved performance in Ohio is not great news for Kasich, who continues to resist pressure from his party to endorse a candidate he "just can't" get behind. As of late September, the governor is sticking with his principles, despite what it could mean for his future career prospects.