It's the Progressives who have had their way, and it's just about exactly for 100 years. That's when they rammed through an amendment to the USC that Senators had to be elected by popular vote--turning it in effect into a national election based on statewide and national issues--instead of by state legislators responsible to the interests of local constituents.
In parallel, the authority for the election of the President has been in effect removed from state electors (the system spelled out in the USC) and subjected to a popular vote, which is something much more vulnerable to manipulation by concentrated power and money in this country or some other country.
The same logic applies to the party system, which used to be much more strongly locally driven. The Progressives (today's Democrats) have been campaigning throughout the 20th century to get party nominations out of the hands of county and state delegations. Within the Democratic Party, they've succeeded, and turned that party from a half-conservative one into a nationally based, Maoist cultural revolution driven by Communist billionaires like Soros and today's metrosexual info-barons.
The Left--and their Communist forebears--have always used outside money to move political movements, starting with Lenin in 1917 with money from the German Empire. In the U.S., their tactic is to have everything decided by mass primaries where essentially anyone from either party can vote. Elections are much easier to buy, and voter fraud much easier to commit, the bigger they are, and the less well all the players know each other. And of course, the effects of one victory are more far-reaching.
As every political observer since the Greeks has recognized, democracy is what leads most directly to tyranny, since tyranny is enabled by mass panic and delusion, which allow it to trample on individual rights to further its own power.
Representative government keeps local priorities at the top of the agenda--which are the things by which people actually live. Panics and the creation of a ruling class in D.C. are slowed down when legislators have reason to fear showing their faces back home.
The outrages that Trump (and Cruz and Lee and Paul) have been speaking against are the creation of the popular-vote political system. To take a key example, only a nationally based and corrupt Chamber of Commerce would try to remove our border with Mexico. The local chambers of commerce in southern Texas, New Mexico, and Arizona would never have put up with such a thing. They'd show up with guns. They live there!
If you love liberty, love political parties with their thousands of messy local meetings and their neighbor-to-neighbor campaigning. They keep things rooted in physical reality, and save the country from big, vapid, ideals for which someone else far from the guarded mansions of the powerful pays the price.
This is a viewpoint I've seen from a number of people on FR. They have decided that the people who are involved in the day to day workings of the party, are the people who should decide the candidate. "The Party members have superior knowledge of the Issues, and therefore have the right to guide the Masses into Correct Thought". That was also the viewpoint of the Communist Party members versus "the masses". These Party members do not see themselves as servants of the Republican electorate.
We need a long-term campaign to purge the party of these elitists.