"The two sides look similar, but there are subtle differences," he said. The brains of nonrighties are more symmetrical and there is "less of a distinction."
An estimated 97 percent of all people have language in the left hemisphere. But, in those who are left-handed and ambidextrous, only 70 percent have language on the left side. The remaining 30 percent have it on the right side or in both hemispheres.
There is no problem with having the hemispheres reversed, but problems can occur when they are "less lateralized or co-mingled," said Klar.
The incidence of neurological disorders like schizophrenia, bipolarity or autism can be three times greater in nonrighties, he said.
But at the same time, with two sides of the brain handling language, the left-handed and ambidextrous can have more complex reasoning.
That may have been the case with some former presidential lefties, according to Richard Norton Smith, scholar in residence at George Mason University, who serves as a consultant for ABC News.
Clinton earned the "Left Hander of the Year" award from Left Handers International when he was elected in 1992.
"That is someone who can break a lot of rules," Smith said. "If lefties are in any way impaired when it comes to communications skills, that doesn't apply to Bill Clinton. He had more of the raw talent of anyone of his generation, and the historical debate will go on for a long time whether he made the most of them."
Reagan once told Left Handed Magazine that he had been born left-handed but switched to his right hand as a result of parental and school pressure. Smith, who served as director of the Reagan Library, said that made sense.
"Reagan transcended the rules and basically wrote his own," he said. "A man who can write with either hand is probably a man who cannot fit any pigeon hole or label. Now that we know more about him, we learn what a complex and subtle figure he was."
Bush Sr. also had more of the right-brain personality, according to Smith.
"He was not naturally eloquent but had extraordinary people skills," he said. "He will be remembered for his diplomacy and restraint. He had an interesting sense of Yankee understatement — his mother was famous for saying, 'People don't like a braggart.'"
Hoover, remembered as one of America's dullest presidents, was also a lefy, according to Smith, who at one time ran his presidential library.
"He was an engineer and thought in very spatial terms," said Smith. "He was very rational, and his thinking was forever reduced to numerical formulas."
Still, there are exceptions. Ford, a lefty, was lampooned for his clumsiness.
Being left-handed has other advantages. Combat, for instance, according to the University of Montpelier in Britain. Southpaws reportedly have more endurance and an edge in fencing, baseball and tennis.
The study speculated that this trait might hold true in other aggressive contexts, such as war. That might not explain George Bush, who is a righty.
Still, Smith is skeptical of putting too much weight on handedness — at least in this election.
What do Obama or McCain bring to the current campaign that their right-handed opponents Hillary Clinton and Mike Huckabee do not?
"Absolutely nothing," said Smith. "Except they may refer to them as 'lefty' for reasons other than their handwriting."