What is the RNC's doomsday plan?

[SteveRogers]

Let's say it's June 2016 and after a long primary battle it looks like Donald Trump will in fact win either a majority or a strong plurality of delegates. Does the RNC have a plan in place to either try to deny Trump the nomination outright or minimize the damage to the party in this scenario? Does Reince Priebus have people working up a "doomsday plan" right now to respond to a Trump win?

Is there any way the RNC could wrestle the nomination away from Trump at the convention?
Would they try to force an unwanted running mate onto Trump's ticket?
Do any major establishment players back some kind of mainstream conservative third party ticket (knowing this will lose Republicans the election but possibly minimalize down-ballot damage)?
Would most sitting Senators and Governors bite their tongues and endorse Trump, or would many refuse to do so?
Could any state parties refuse to give Trump their ballot line? 

[SteveRogers]

Just accept that Hillary or Biden will be POTUS, and hope that Trump does not take down two many Pubs in Congress with him.

If that's the case, then is there a way for Republicans to minimize the down-ballot damage?