The former mayor of New York is reportedly 5 foot 8 inches tall which is only a tad under the 5-foot-9 national average for U.S. males, according to the World Population Review, but this does not stop Trump from repeatedly dubbing him “Mini Mike,” on Twitter and in rallies.

On February 13, Trump even exaggerated what he believes is Bloomberg’s lack of height, tweeting: “Mini Mike is a 5'4” mass of dead energy who does not want to be on the debate stage with these professional politicians. No boxes please." Bloomberg’s campaign says there is no truth to the president’s claim about the need for a box.

Trump’s barbs could be because at 6 foot 3, he is the third tallest president ever, behind Lyndon Johnson’s 6 foot 3½ and Abraham Lincoln, who at 6 foot 4, was not just a towering historical figure.

Seven inches shorter than Trump is Bloomberg who, should he win the race to the White House, would be the most diminutive U.S. head of state since 5-foot 7-inch William McKinley, who was assassinated in 1901.

“Trump towers over the guy—I don’t think that helps Bloomberg,” says Gregg Murray, professor of political science at Augusta University in Georgia who researches how people vote and authored a study into the link between physical formidability and leadership.

On his constant “mini-Mike” barbs, Murray told Newsweek: “You know what the schoolyard is like for boys and there are times that Trump exhibits schoolyard behavior.”

It is true that history is not on Bloomberg’s side. There have only been six presidents who were shorter than him, two of whom were founding fathers—John Adams [5 foot 7] and the shortest ever president, James Madison [5 foot 4], who served in office well before television was a conduit to the electorate.

Of the 58 U.S. presidential elections, the taller candidate won two-thirds [67 percent] of the time and the winning candidate was taller than the average American man 81 percent of the time, Murray says.

“For a lot of people who don’t follow politics too closely, their decision between two candidates may come down to ‘who looks more like a leader?’”

“If you think about what national leaders are asked to do, their primary function is protect the existence of the country and one of the primary threats to the country are invasions from other countries to occupy and take over the country.”

This feeling has been hard-wired into humans since when they were hunter-gatherers and a leader who was more physically formidable to defend a tribe’s vital resources was looked upon more favorably, Murray says, “having a big guy to jump on your side was really useful.”

“I think that is what is going on internally when we think about a preference for physically formidable leaders, that plays into what we think national leaders should do.”

Still, Bloomberg does not have to look too far back to see that height is not everything. In 2012 Barack Obama [6 foot 1] beat Mitt Romney who was an inch taller.

George W Bush [5 feet 11 and a half ] beat the height odds in both 2000 and 2004, despite being an inch and a half shorter than Al Gore and a four and a half inches shorter than John Kerry.

However Bloomberg would have to go back almost two centuries ago for the last time a similar height disadvantage that he has with Trump was overcome. In 1824, John Quincy Adams [5 foot 7½] beat three candidates, who were all over six feet.

More recently, but still over a century ago, Benjamin Harrison [5 feet 6 inches] defeated Grover Cleveland in 1888, who was five inches taller.

Murray notes that taller people tend to be leaders because of a lifetime of positive feedback. The female Democratic contenders for 2020, Elizabeth Warren and Amy Klobuchar are both 5 foot 8, four inches taller than the average American woman.

“They tend to think because they have been told they look like a leader, they think they are more qualified to be a leader and therefore more likely to put themselves forward,” said Murray.

Newsweek has contacted the Bloomberg and Trump campaigns for comment.