Who is a RINO?

With all of the John McCain talk buzzing around, I'm hearing the term "RINO" ("Republican In Name Only") thrown around a lot lately. RINO is a term that has changed in meaning over the last several decades. The scope of my life isn't long enough to recollect it myself (I was born in the late 1970's, but I only remember Reagan). Wikipedia has a decent article outlining who has traditionally been considered RINO within the Republican Party and for what reasons. You might be surprised... or you might not:

From 1936 to 1976 the liberal side of the Republican party frequently won the national nomination with candidates such as Alf Landon, Wendell Willkie, Thomas E. Dewey, Dwight D. Eisenhower, and Richard Nixon, and Gerald Ford. Indeed, other terms for Liberal Republicans include Nixonian and Rockefeller Republican. The mainstream of the party was generally supportive of the New Deal, and the conservatives were the RINOs.

Soon, Reagan came along and how many initially took him seriously?

After 1980 there were few if any open liberals in prominent positions in the GOP, except for numerous "moderates", such as George H. W. Bush, who had run for president on the stance that Reagan's Conservative platform was "voodoo economics".

And then, when I think of RINO today, I think of folks along the lines of pro-choicers Giuliani, Bloomberg, etc... but then McCain doesn't quite fit that mold, at least not in the same way. And who else has held the RINO label? Romney, Huckabee, and Ron Paul.

This election, who isn't a RINO? Perhaps we should redefine what the "Republican Base" truly entails. Yelling and screaming from folks like Ann Coulter and Rush Limbaugh isn't helping very much.