(The Wall Street Journal, Andrew Hinderaker, Pool/Associated Press) Democratic mayoral candidates for New York at a televised debate on Tuesday, Sept. 3. From left are Anthony Weiner, Bill Thompson, Bill de Blasio, Christine Quinn and John Liu.

The tumultuous Democratic primary race for New York's first new mayor in 12 years is nearing the finish line. There are only a few days left until Democratic voters take to the polls on Tuesday, and after the implosion of Anthony Weiner's campaign and a poll that has Bill de Blasio surging to a commanding lead, the city's public advocate currently looks like he has the advantage with voters.

And it appears there's another advantage for de Blasio: He's tall. And I mean really tall--the kind of tall that makes writers who profile him use it as a metaphor for his high-minded liberalism. At 6-foot-5, de Blasio towers over his competitors. The photos from the debate Sept. 3 say it all: de Blasio is at least a head taller than his opponents, and his position in the center of the room only accentuated his height.

Does that matter? Maybe not so much in New York. The city has had its share of short-yet-powerful mayors, and New York mayors' height has famously been questioned in the past. But in general, a tall stature usually--if subconsciously--confers an advantage when it comes to being picked as a leader.

We'd like to think the measure of a person's body matters little when it comes to measuring his or her capacity to lead. But plenty of research confirms that "height-ism" really does exist. One recent study showed that 58 percent of presidents elected were taller than their opponents (the researchers threw out 11 elections for lack of data or height differences), and that 67 percent of the winners of the popular vote were taller. A 2011 study by psychologists at Texas Tech University found that when asked to draw the "ideal national leader" alongside an "average citizen," 64 percent of study participants drew the leader as the taller figure. The rationale is simple, the authors say: We choose tall leaders because of caveman politics. It's evolutionary forces at work.

Similar results have been found in the business world. A study from 1990 found that people in management positions were taller than the people who worked for them. Similarly, a more recent study of men in Sweden found that an increase in height by 10 centimeters is associated with a 2.2 percentage point increase in the likelihood of being a manager. And in Malcolm Gladwell's book "Blink", he reports that more than half of U.S. CEOs at the time were at least 6 feet tall--with 30 percent being 6-foot-2 or greater. Compare that to the general population, where just 3.9 percent of adult men are of similar height.

If de Blasio wins the primary Tuesday--and that is hardly certain--it will likely be for how well he has distanced himself from the Bloomberg era and focused on inequalities, all while airing memorable ads and watching Weiner-mania implode amid further sexting scandals and verbal sparring with voters. It won't, of course, be directly attributable to his height. But in a wide-open field where a de Blasio win was once unthinkable, research shows it probably hasn't hurt him too much, either.

Jena McGregor is a columnist for On Leadership.

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