Would the same thing happen to Kasich in your opinion?
Yeah I think so. Kasich lost in 2016.
I think all the Republicans that scoffed at Trump's chances in 2016 are pretty damaged. I mean the ones that really went at it - like Romney, Ayotte, Heck, Kasich, Jeb!, etc. etc.
Kasich would get destroyed in Iowa, and he'd barely make a dent in New Hampshire. I think he'd do 2% in Iowa, and 15% in New Hampshire (same as Romney).
IF Trump is going to face a serious challenger, I don't think it will be from a candidate that has ran before. It'd have to be someone entirely new and not vetted/embarrassed by Trump. Trump would clown Kasich if Kasich ran. Romney would be Jeb! 2.0.