Alex Campbell says, " I have heard you mention a few times that if Trump wins the nomination, he will destroy the GOP. I was hoping that you could say more about what exactly you mean by this and why you think it." Let me try to respond.
Both the Democratic and Republican Parties rely for electoral support on what is referred to as their "base," which is to say a sizeable group of voters who can be counted on, in good times and bad, to vote for the party. Since only between 54% and 62% of eligible voters have actually gone to the polls in the past four cycles, it is obvious that "turning out your base" is a key to winning a presidential election. A solid margin of victory in a presidential campaign is perhaps three to five percent of the total vote, so there is more to be gained by increasing the share of your base that votes than in persuading so-called "independent" voters to switch from one party to the other.
For half a century now, those who run the Republican Party have been successful in getting a base of low and middle income voters to support policies that benefit the rich rather than themselves by appealing to racial prejudice, religious anxiety, resentment at class snobbery, and jingoist passions. As Thomas Frank put it brilliantly in his 2004 book What's The Matter With Kansas?, the Republicans get the peasants to charge the castle with pitchforks, shouting as they charge "We are mad as hell, and demand that you cut taxes on the rich!"
The Republicans never deliver what they promise on social issues, but fears about same-sex marriage, abortion, and the "War on Christmas" keep the base riled up and in line.
This seems to be the year in which that con job finally fails. Trump has hi-jacked the Party while making it clear that he cannot be counted on to support international capitalism and the financial classes [it is very significant that Trump is in construction, which is typically local, not international.]
The merger of the interests of the rich and the anxieties of the lower middle class has never been natural or stable, and if Trump does in fact win the nomination, it is difficult to see how that merger will be reestablished after he loses the general election. It is noteworthy that the super-rich individuals who have poured hundreds of millions into the Republican Primary Campaign have thus far had virtually no return on their investment.
Something like this is what I had in mind.