Close your eyes and picture the face of the person you think will win the presidency in 2012. Do you see a smile or a scowl?

According to research by Professor Albert Mehrabian of UCLA, how much we like a communicator depends on the “congruence” of three factors—words, tone of voice and non-verbal behavior. Fifty-five percent of what influences our judgment about that “fit” is non-verbal: the speaker’s eyes, face and an “attitude” that comes across in the body language.

When two (or more) candidates “face off” in a general election for president, history shows that the winners are the “congruent” grinners—those whose smiles, combined with their positive messages, inspire rather than irritate voters.

That was the case in 2008 when Barack Obama’s grin, combined with his consistent “hope and change” message captured the imagination and matched the mood of the public.

Obama’s smile beat John McCain’s grimace, as McCain’s messages (and mouth) flapped around in the final months of the election, from “the fundamentals of our economy are strong” to our economy is in “a total crisis.”

In 2004 and 2000, George W. Bush alternated between a smirk and a cocky smile. But even those mixed facial expressions—and Bush’s messages of strong leadership—provided the “grinning edge” over his mirthless opponents, the terminally serious and insufferably pompous John Kerry and Al Gore.

In 1996 and 1992, Bill Clinton flashed a jaunty smile and a relentless “man from Hope” personality. His leadership accomplishments—first as a governor then as a president—showed a willingness to find a “third way” between warring Democrats and Republicans.

In 1996, scowling, ranting Bob Dole didn’t have a chance against Clinton’s sunny smile and Clinton’s confident insistence that he had put America on the right track.

That same year, Reform Party candidate Ross Perot’s bizarre smile and angry manner made Clinton look even better by comparison.

In 1992, against the strained smile of President George H.W. Bush and the weird rictus of alarm of the insurgent, Perot, Clinton likewise looked every bit the winner. Bush couldn’t believe that a scandal-plagued politician nicknamed “Slick Willie” could shuck and smile his way past the storied Bush résumé. But Bush had his own “congruence” problems when voters read his lips and saw how he broke his “no new taxes” pledge.

When George H.W. Bush won his single term in 1988 his frenetic grin was positively endearing when contrasted with the mechanical smile and robotic messaging of Michael Dukakis. Plus, Bush had the advantage of surfing on Ronald Reagan’s golden legacy, having served as "The Gipper’s" vice president.

The secret of a winning presidential smile isn’t just in the mouth. Presidents also smile with their eyes, showing inner warmth or an amused twinkle, for example. Voters can detect the difference between the verbal and non-verbal communication of a Happy Warrior versus an Unhappy Worrier.

Reagan’s smile and sparkling Irish eyes—plus his leadership record—were unbeatable, especially when matched against the dourness of his two opponents in 1980 and 1984, Jimmy Carter and Walter Mondale.

When Carter defeated Gerald Ford in 1976, Carter’s smile was still seen as country-fresh and an antidote to the lingering national nausea over Watergate. Carter’s smile hadn’t yet morphed into looking like a “Mr. Peanuts” cartoon grin—as it did in 1980, with the caption under Carter’s face reading, “Malaise.”

Even Richard Nixon—“Tricky Dick”—calibrated his smile and focused his darting eyes with the fervor of commitment when compared to his two wimpy opponents in 1968 and 1972, Hubert Humphrey and George McGovern.

In a presidential contest, whoever appears more upbeat is victorious over whoever seems more uptight.

Today, President Obama looks—and sounds—uptight. He complains that America “has gotten a little soft” and “we've been a little bit lazy, I think, over the last couple of decades." An air of desperation has crept into his face, eyes and body language as he exhorts even his African-American base supporters to, “Stop complainin'. Stop grumblin'. Stop cryin'.”

Obama’s eyes, face and message have lost the glow of 2008 and they certainly don’t evoke his presidential heroes, the grinning and winning John F. Kennedy and Franklin D. Roosevelt.

To beat Obama in the general election, Republicans must select a candidate with both a verbal and non-verbal message that by comparison with Obama’s, packs the power of a smile—and puts a smile on the faces of a majority of voters.

Communications consultant Jon Kraushar is at www.jonkraushar.net.