One of my new favorite people is Curly Hoagland, a long-time member of the Republican National Committee and unpledged delegate from North Dakota who has had his fifteen minutes of fame lately on cable TV. Hoagland's shtick is to quote the rules of the Republican National Committee concerning the selection of delegates to the July Convention and then to say, ominously, that we shall not know who actually has 1237 delegate votes until the first ballot is taken at the convention. The current primary contests, he says, are just "beauty contests."
So I took a look at the rules of the Republican National Committee. Here is Rule 16(d)(2):
"Only persons eligible to vote who are deemed as a matter of public record to be Republicans pursuant to state law or, if voters are not enrolled by party, by Republican Party rules of a state, shall participate in any primary election held for the purpose of electing delegates or alternate delegates to the national convention or in any Republican caucus, mass meeting, or mass convention held for the purpose of selecting delegates to the county, district, or state conventions, and only such legal and qualified voters shall be elected as delegates to county, district, and state conventions; provided, however, that in addition to the qualifications provided herein, the applicable Republican Party rules of a state may prescribe additional qualifications not inconsistent with law, which additional qualifications shall be adopted before October 1 in the year before the year in which the national convention is to be held and published in at least one (1) newspaper having a general circulation throughout the state, such publication to be at least ninety (90) days before such qualifications become effective."
A number of the Republican primaries allow Independents and even Democrats to vote, and the exit polls indicate that Trump has been winning large majorities or pluralities of those voters.
Curly has a point.