The GOP has what I see as 4 options here, assuming Trump has the plurality or majority of delegates.
1. They get behind Trump, try to win and mostly get crushed. This will result in both a "see, we told you so," and "we need a real conservative" bullshit again. Hopefully, 2020 ends with a "real conservative" ala Cruz getting crushed and then they finally reform the party more moderate.
2. They allow him to run but don't really give him much support, try to salvage what they can by pushing for other races. They get crushed but perhaps salvage the House and maybe the Senate. Mostly the same outcome as #1 but perhaps a bit riskier short-term if lose the House/Senate as a result
3. Brokered convention and steal it from him. This is the riskiest path and guarantees, imo, both a loss in the Senate and WH and probably even the House. Trump's avid supporters would stay home or vote Dem out of spite. I don't even think this is a real option for them. Would destroy the party short term and long term.
4. Run 3rd party against him. This is the most interesting choice. They'd definitely lose in 2016 but might salvage the House. It would also be a longer term strategy to reach out towards non-Trump voters. But it could just as well piss them off like in #3.
Basically, I see 2 main scenarios. Either the GOP battles itself in 2016 or does so right after 2020. They have to pick when to rip that band-aid off.
BTW, I really don't understand Kasich's philosophy. He's no competitive tomorrow and is waiting for Ohio to be the not-Trump. But he's going to be so behind in delegate math by the time Ohio votes that even if he wins it, where does he even stand to win? What's his path?
Unless he's hoping Trump collapses to like 15%, I don't get it.
None of these guys are doing anything right.
I do expect Carson to drop out after tomorrow night, though.