The assumption that we prefer taller presidential candidates has become modern gospel. But is it valid? Not exactly. Since 1972 alone, three shorter candidates have won the presidency: Richard Nixon, Jimmy Carter, and George W. Bush (twice).

This isn't to say that physical stature doesn't matter politically. In the upcoming presidential campaign, as in so many, the relative size of candidates will be taken into account along with their positions on gay marriage and free trade. Height matters. But the way it matters is far more nuanced than we might imagine.

At the upper end, if handled gracefully, tallness can enhance an aura of presidential stature. Our consensus two top presidents – George Washington and Abraham Lincoln – stood well over six feet tall. Little John Adams once complained that Washington, like King Saul, was "chosen because he was taller by the head than the other Jews."

There is no inherent advantage to being tall, however. Some smaller candidates capitalized on their short stature by creating a feisty persona. Think Teddy Roosevelt. Think Harry Truman.

During his campaigns for the presidency, George W. Bush successfully leveraged his less-than-6-foot stature into an image for himself as one of the folks, not a wealthy product of Phillips and Yale. When confronted with two taller opponents, Mr. Bush wrapped himself in the little guy's mantle: often underestimated, seldom vanquished.

During the debates in 2000, it was assumed that Texas' governor would be demolished by the taller, smarter, better informed Vice President Al Gore. Just the opposite happened. Mr. Gore's condescension, sighs, and larger size created sympathy for his smaller opponent. When Gore strode across the stage to hover over Bush for no apparent reason other than to call attention to their height disparity, anyone who's ever had to confront a glowering bully identified immediately with his opponent.

A similar situation helped Bush undercut John Kerry four years later. Senator Kerry's commanding 6 foot, 4 inch height reinforced his popular image as an aloof Brahmin, above it all, talking down to his smaller opponent, and – by implication – the rest of us.

Unusually tall men such as Kerry then, and 6 foot, 5 inch Fred Thompson today, must learn how to put at ease those straining to make eye contact with them. Mr. Thompson's laconic manner is an asset in this regard. It tempers his tallness.

During the 1988 vice-presidential debate, big Lloyd Bentsen took a different tack. Without being overtly imperious, Mr. Bentsen patronized Dan Quayle just enough to make his smaller opponent shrink in stature. Eight years earlier Ronald Reagan did the same thing to Jimmy Carter. ("There you go, again.")

Until Mr. Reagan cut him down to size, President Carter had effectively dealt with his short stature by implying that he was larger. Rather than stand ramrod straight, like a strutting banty rooster, Carter slouched a little – as if he had an inch or two to spare. That's why it took us a while to realize just how short Carter was (5 feet 8 or so).

Having to stand beside 6-foot Gerald Ford blew his cover. On the eve of his 1976 debate with Mr. Ford, Carter's negotiators first demanded that the two stay seated. Losing on this point, they settled on having the candidates' lecterns placed far enough apart that the difference in the two men's size wouldn't be so apparent. (In return the Democrats agreed to a background pale enough to camouflage Ford's lack of hair.) When the two finally squared off, Carter made their moment of physical proximity as brief as possible – sticking his arm out stiffly to hold the president at bay, grasping his hand momentarily, then dropping it like a live hand grenade before scurrying to the safety of his lectern.

Who today is managing his or her height effectively? With her calmly assertive manner, Hillary Clinton looms larger than her mid-five-foot stature might warrant. As a war hero John McCain – who is not much taller than Hillary in heels – needn't worry about bringing diminutive Michael Dukakis to mind. Senator McCain also comes across as feisty, a fighter in the mold of his hero, Teddy Roosevelt. By contrast, six-footers such as Barack Obama and Mitt Romney can relax and let their height speak for itself.

For the sake of the American electorate, the best matchup next fall might be Clinton-McCain, or Obama-Romney. Such contests would effectively neutralize height as a campaign concern. Clinton-Thompson, on the other hand, would be a horse race of a different color. Whether Senator Clinton could cut her far taller opponent down to size would be a test of her ability to project strength, just as Thompson's ability to call attention to his stature without looming like a bully would be a measure of his political agility.