Dwight Eisenhower and wife Mamie.

ABOARD THE CNN ELECTION EXPRESS IN PLACENTIA, California (CNN) – On a journey like this you learn some valuable life lessons, and so far I certainly have.

For example, here is how to spend the best three dollars you will ever invest:

If you are dining at a Denny’s, and, before ordering, you turn over the menu to find that the same meal you were about to ask for is available at a senior discount. . . .

And if the terrible, icicle-claws-in-your-stomach realization dawns on you that you are, in fact, available for that discount. . . .

Don’t do it. Order the regular meal. The three dollars you’d save is not worth the despondency that would result from having the qualifying conversation with the waitress. Pretend you didn’t even see the back of the menu. Proceed as if it doesn’t apply to you.

Another lesson, not quite as personal but just as apt, is this:

For anyone in America who wasn’t around in 1952 — meaning most of the country — the presidential election this November is going to be like none they have ever experienced.

Much has been made of that fact that the Bush family and the Clinton family have put the word “dynasty,” more often used to describe royalty or successful sports teams, into the forefront of the American political vocabulary. But, whether or not Hillary Clinton becomes the Democratic nominee and then the president, there is something else about this year’s election that makes it extraordinary: the 1952 factor.

This November will be the first time in 56 years that neither of the candidates for president has already served as either president or vice president.

In 1952 it was Dwight Eisenhower vs. Adlai Stevenson. After that, there has never been an election lacking a candidate who had previously been No. 1 or No. 2 in the executive branch.

To save you from doing the memory gymnastics: In 1956, Eisenhower was running for re-election as the incumbent. In 1960, his vice president, Richard Nixon, was a candidate. In 1964, Lyndon Johnson — the sitting president, who had been John F. Kennedy’s vice president — ran on his own. In 1968 Nixon was back on the ballot against Johnson’s vice president, Hubert Humphrey, and in 1972 Nixon ran as the incumbent. In 1976 Nixon’s second vice president, Gerald Ford, ran, and in 1980 the man who defeated Ford, Jimmy Carter, ran as the incumbent. In 1984 the sitting president, Ronald Reagan, ran against a former vice president, Walter Mondale. In 1988 Reagan’s vice president, George Bush, ran and won, and in 1992 he ran and lost. In 1996 the sitting president, Bill Clinton, ran — as in 2000, did his vice president, Al Gore. In 2004, the man who defeated Gore, George W. Bush, ran for re-election.

It has become all but required, the idea that one of the candidates must have already served in the White House. If you’re 55 years old or younger, it has never been any other way in your lifetime.

So for most Americans, this is new territory. Now, there is another similarity between the 1952 election and the one this year, even though the major parties have not yet named their candidates. One of the candidates in 1952, while not having served as president or vice president, was as well-known to Americans as any politician: Eisenhower had great stature as a World War II hero, and he amiably grinned a beaming Ike smile around the country on his way to a landslide victory. This year one of the two leading candidates for the Democratic nomination, Hillary Clinton, has been known for a decade and a half to virtually every citizen because, although not elected to the White House, she lived there for eight years. Both Eisenhower and Clinton brought immense, saturation celebrity to their candidacies.

The most striking thing about the uniqueness of this year’s election — at least the uniqueness in the prism of the last half-century — is that not much is being made of it. For whatever reason, Americans have, without really thinking about it, long demanded — or taken on faith — that one of the two candidates in a November election be someone who has been the president or the vice president. It’s as if there was some sort of comfort, or sense of security, in that. This year, mostly by circumstance, the nation has changed its mind. And barely discussed it.

Soon I will tell you about an oddly obsessive restaurant out here — not a Denny’s — where the gimmick is garlic, but for now I can’t get out of my mind the image of Eisenhower smiling. As soon as I typed that reference to it two paragraphs above, I couldn’t stop thinking: Ike’s grin was almost exactly the same as Hillary Clinton’s. Close your eyes and think about it. Coincidence? Or Mystery of History?

Tomorrow: a tale of garlic ice cream.

Bob Greene is an award-winning journalist and best-selling author.