You need to take this on an issue-by-issue basis in order to give the topic justice.
1. Taxes: The GOP has always emphasized small government, but it was far more interested in balanced budgets than in tax cuts prior to Reagan. Even Reagan didn’t consider tax cuts to be the object of religious veneration. When Bush 41 lost the 1992 election after breaking his promise on tax increases, however, the party concluded that all future increases of any kind were anathema, and that tax cutting was the very essence of being a Republican. Nothing about that has changed since the early 90’s; if anything, the tax cut proposals have become more and more irresponsible over time.
2. Crime and social issues: Richard Nixon wrote the playbook on these issues, which haven’t changed much in 40 years.
3. Nihilistic legislative tactics: Newt Gingrich was the innovator here. Ted Cruz and the Freedom Caucus are just his disciples.
4. Climate change: John McCain supported cap and trade in 2008. That seems like a long, long time ago.
5. Attacks on “free stuff” for the poor: Some of this came up during the debate on welfare reform during the Clinton Administration, but Bush 43 was a “compassionate conservative.” Since 2008, we have had “conservatism” without the “compassion.”
6. Militaristic foreign policy: Prior to the late 1960’s, it was the Democrats who believed more firmly in foreign military adventures. That changed during the Nixon Administration. The parties are still, in some ways, fighting the battles of the late 60’s and early 70’s.
7. Entitlement cuts: A serious conversation on this subject started during Bush 43, but has accelerated dramatically since 2008. Entitlement cuts are now the orthodox position within the GOP.
As you can see, there are a few issues on which the GOP position has not changed much since the 1960’s, but in most cases, its stance has hardened substantially since the beginning of the Clinton Administration, and particularly over the last several years. I will discuss the reasons for this tomorrow.