Texas will be a huge test. Cruz needs to take Texas, where things are a bit confusing. They have a "graduated" system for the majority of their delegates.
https://www.texasgop.org/wp-content...egate-Selection-Process-to-GOP-Convention.pdf
So, if Cruz can get better than 50% in individual districts, he denies Trump those delegates. If he gets less than that, he'll probably have to concede at least 1 delegate.
https://www.texasgop.org/wp-content...egate-Selection-Process-to-GOP-Convention.pdf
Of the three delegates allocated for each of the 36 congressional districts (108 in total):
If a candidate receives a majority of the vote (more than 50%) in a congressional district that candidate is allocated all 3 of the district’s delegates
If no candidate receives a majority in a congressional district, but at least one candidate receives 20% or more, the candidate with the most votes (plurality), receives 2 delegates and the next highest vote getter receives 1 delegate.
If no candidate receives 20% in a congressional district, then the top 3 vote getters each receive 1 delegate.
So, if Cruz can get better than 50% in individual districts, he denies Trump those delegates. If he gets less than that, he'll probably have to concede at least 1 delegate.