If Kasich, Bush, and Huckabee drop out then the GOP has no one with enough experience and a good enough record. Will not support anyone else, might as well just let Hillary win if the GOP nominee is not one of those three.
A recent poll asked what is most important to voters. 12% said experience. The majority said they wanted someone who would change Washington. Kasich is a victim of the current mood among Republican voters. I don't blame voters. Conservative politicians with experience have failed to stop abortions, illegal immigration, runaway spending, gay marriage, growth in poverty, people dropping out of the work force, growth in numbers of people on food stamps, growth in all entitlement spending. So why is experience such a critical factor? Voters want new blood to shake things up. They don't feel inexperience candidates can do any worse than the experienced politicians have been doing.