Maybe in the Western states, but in the Northeast, Kasich is more of a real threat to Trump than Cruz. Kasich will limit the number of delegates Trump would otherwise pick up in states like PA, CT, RI, and perhaps even NY (none of which are winner-take-all).
Kasich should be limiting his campaigning to those NE liberal states and not campaigning in the West where he is running a very distant third. Similarily, Cruz should not campaign in the liberal NE states where he runs a distant third. That is the way to deny Trump enough delegates and force a contested convention. I am not sure why all the candidates are unwilling to coordinate and win.
How? He's unknown outside Ohio, he's already ran for shit in not one but two bordering states (3rd in Michigan, 4th in Kentucky, and not carrying a single county in either one), and he has no money. He won't break 10% anywhere up East.