Romney was popular only by default. Conservatives weren't in his camp until Romney was only semblence of a conservative left in the race. I strongly doubt many of these reluctant converts will enthusiastically support him if there are real conservatives running.
The last 11 elections (beginning in 1964 when the conservative movement really got started) just don't provide very strong evidence for this theory. Four nominating processes are not applicable since there was a popular incumbent Republican President who was essentially unchallenged: 1972, 1984, 1992, and 2004.
Three primary election cycles argue against that theory. In 1964, the outsider clearly won in Goldwater much to the chagrin of the Republican establishment who supported Nelson Rockefeller (a group which included the Romney family). In 1976, although Ronald Reagan didn't win the nomination, his candidancy showed that the Republicans don't always vote for the next guy. As the sitting President, Gerald Ford would rightfully claim the next-guy-in-line title. In 2000, George W. Bush won in a year that there wasn't a clear claimant to the title of the next-guy-in-line.
Four primary election cycles argue in favor of this theory: 1968 (when Richard Nixon re-emerged), 1980, 1988, and 1996. In these years, the Republican nomination was given to the guy who had paid his dues.
Overall, I think the tally is 4-3-4 on the theory which isn't real strong support. After 2008, it is likely to be 5-3-4 which still isn't very overwhelming evidence. It certainly doesn't make it a lock.
Wow a smart poster. I’m so pleased to read something actually intelligent. Good for you. Let’s all support Newt Gingrich for President in 2012 and make the “next guy in line” fraternity die once and for all. We can do it if we are united and if Newt will JUST RUN !