I think that the premise of this article is bogus. Political Parties can select their party nominee in any number of ways, subject to certain rules about gaining to each state’s ballot and certification that the nominee is qualified for the Office of the President. No one has a right to vote for a party nominee, although a state political party may choose to hold a primary election, and then may choose how to conduct the election subject to state laws.
Recall that Ross Perot run as an Independent in 1992 and used a grass roots organization to get his name on the ballot in all 50 states. There were no primaries. In 1995, Perot formed the Reform Party, but they did not have a convention, and they held a primary based on mailed ballots to those who had qualified as members of the Reform Party. Perot was nominated and once again, he qualified for the ballot on all 50 states, although in some states, he had to file as an Independent.
We tolerate this government/political party conspiracy for the purposes of having a state wide primary, but it’s not required and voters really don’t have any rights to participate in the process. Interestingly, everyone used to understand that the primaries were really just “beauty contests” that did not bind the parties or the delegates to their convention. We now have a later generation who believe that they have a right to vote for the candidate of their choice in a primary and that their political party is obligated to nominate whomever the primary voters selected. That has always been a fiction, but was encouraged by the parties who wanted to present unity to the TV audience at the national conventions. Of course, the real outcome has been to plant a false expectation among voters, decimate the TV ratings, and reduce the powers of the political parties. The liberals and the media have be the beneficiaries of this evolution of our election process.
http://www.nationalaffairs.com/publications/detail/a-republican-nomination-process
You may be interested in the above link which was written after the failed 2012 election. It goes into some of the old history of the process, more recent changes in the 1970’s (which you mention), the mess we are in now, and some possible fixes.
My summary of the article is that our process now leaves our contender bruised, bloodied and broke before the Main Event even gets started.
Yet this is why we have the mess we are now in with regard to the primary voting process.