That's not where their problem lies. "How do they set up a system where a candidate with less than 40% of the party supporting him cannot get the nomination" is the real question, especially because of how difficult concerted reforms to the primary system are to pull off and more especially because depending on what direction they take the reforms some factions of the party will see themselves becoming more or less empowered.
Ted Cruz got second, so there's clearly a problem...
Ideologically, I don't find Cruz in second to be much of an issue. Regardless, a fair system would remove the influence of early states and remove the possibility of a nominee being selected through vote splits -- say, by a nationwide instant-runoff election. I am basically certain Trump would not have been the winner of such an event, and nearly certain that it would not have been Cruz either.
