I was doing some research into Ronald Reagan's 1968 run for president. I discovered that only 12 states and DC held Republican primaries (map). In 1964 Texas and Florida both held Republican primaries (map) and Goldwater won both.

Reagan's popularity among conservatives began when he did this 1964 speech for a Barry Goldwater fundraiser. The only states Goldwater won in the general election were Southern states and his home state of Arizona. I'm curious why Texas and Florida did not participate after doing so in 1964? Also why did no other Southern state want to hold primaries at that time when they voted Republican the previous election?

I've also read that Nixon was kept off the ballot in California thus resulting in Reagan winning the state and getting the popular vote. Why was this done?