Very correct, Lone_Gunman. If JFK, or Hubert Humphrey, or even LBJ were alive and holding office today, they'd have a difficult time choosing a party affiliation.
The lines between traditional definitions of "liberal" and "conservative" have pretty much vanished. Instead, the terms are applied selectively and individually, depending upon who's writing the story or who's running the campaign. John McCain is no more a conservative than Hillary Clinton.
JFK was much more conservative in the traditional sense (taxes, big government) than Rudy Guiliani.
I'm no history wiz, but I suspect that the blurring of the lines began with Reagan's presidency. After that, everyone who aspired to office in the Republican party laid claim to his conservativism. Problem was (and still is) that few are true conservatives.
The 1994 "Republican Revolution" ushered into office some folks who could legitimately be called conservatives: Newt Gingrich and JC Watts come to mind.
Once in office, though, most of them seem to have become preoccupied with staying in office. And they've resorted to the age-old strategy of promising everyone everything at any price.
The distinctions have been further blurred by social issues that I suspect the leadership of both parties would like to see just go away: gun control, abortion, religion, gay issues, etc.
The result is that a Zell Miller is both a liberal and a conservative, and so is McCain.
There are still some traditional conservatives out there. Columnist Robert Novak is one example. As a tax-cutting, isolationist conservative, he's been critical of GW's invasion of Iraq from the outset, as well as the increased spending on social programs.
Pat Robertson might be considered another example, although the Republicans successfully cut him off at the knees after he wrote in his book about isolationism at the outset of WWII. (Another topic for another time).
Within the Republican party now are two wings, and they don't always play well together: the country club Republicans, primarily concerned with taxes and spending; and the social issues Republicans.
For so-called "conservative" voters like me--who want no gun control, want government out of our bedrooms and cars and motorcycles and toilets and wherever else government seems to wander, want spending reduced, want taxes lowered, and want our borders secure--there's slim pickings for candidates.