This is an excellent rant from Steve Schmidt, one of the few Republican stalwarts who are willing to call his party on the deep, corrosive problems within it.
The problem for principled Republicans like Schmidt and a number of friends of mine is that the intellectual fountainhead and patrician leadership of the party couldn't matter less to most of the people who vote Republican. The problem the Party has with Trump this year will not disappear in 2020. Their voters are aggressively anti-intellectual, irresponsibly headstrong and earnestly believe in the manifest destiny of their uncompromising Economic Libertarianism and Cultural Religiosity.
The most important word in that last paragraph is "uncompromising." These people do not tolerate the collegial compromise that kept the government wheels turning for a couple hundred years, despite the nominal philosophical differences between the parties. The intellectual rot in the Republican Party is not a platform issue. It is the ignorant voter base that their policies have kept from adequate education and who were spoon-fed Talk Radio and Fox News for 30 years, dead certain of their rightness, and who will never be convinced to vote for their patrician compromisers ever again.
They have been force-fed the Romneys and McCains and Bushes for generations, and they've had it. They want Trump. If it can't be Trump, it will be Cruz or Pence or someone equally extreme and repulsive to most other Americans.