The leading candidate has always had the RNC’s backing. If Jeb hadn’t been taken out by Trump in S Carolina, none of this would be happening. George H Bush and George W are taking this personally and are out to get Trump.
Period.
If George W supported Trump tomorrow, all this would end. It is the Bush clan along with Romney who are driving this and it is disgusting because they think they are better than everyone.
If a candidate wins a majority of the delegates he'll be the nominee. It's got nothing to do with RNC backing, or with being the "leading" candidate. Leading isn't sufficient. A majority is required.
The Bush clan is too busy supporting Cruz.