Ohio has been trending blue which is why a “Conservative” like Kasich was elected Governor.
Kasich has favorable poll numbers in his home state.
I believe the Ohio Republican Party endorsed Kasich.
Close elections generally come down to turn out. If Trump supporters are the more motivated, Trump will win.
But, if by some stretch of the imagination, Kasich got the nomination, Ohio would need a new Governor.
Kasich is a lame duck governor. He’s in his second term (reelected to a four year term in 2014) in a two term limit State. He’s the odds on favorite to challenge Sherrod Brown for a Senate seat in 2018, unless pigs fly and he becomes president.