Fivethirtyeight: The basic reason is simple. Most of the 2,472 delegates with a vote in Cleveland probably aren’t going to like Trump.
Trump’s delegate problems stem from two major issues. One is his lack of organization: Trump just recently hired a strategist to oversee his delegate-selection efforts; Cruz has been working on the process for months. The other is his lack of support from “party elites.” The people who attend state caucuses and conventions are mostly dyed-in-the-wool Republican regulars and insiders, a group that is vigorously opposed to Trump. Furthermore, some delegate slots are automatically given to party leaders and elected officials, another group that strongly opposes Trump, as evident in his lack of endorsements among them. (read the whole thing)
All the Trump gaffes appear to show a man, as the pundit lingo goes, 'not ready for prime time'. Imagine that. The reason why you don't hear that sort of epithet said about Trump, however, is because it's inconceivable that a man who spent so much time on camera can be said to not be ready for it. And yet... the fact that Trump is not a polished politician is one of the most mentioned charms invoked by his loyal followers. A bit of a catch 22 Trump is.
