We can predict the answer to that question more than the chorus of political analysts might let on. If the outcomes of the last dozen presidential contests are any indication, the answer lies in which candidate boasts the winningest -- or most genuine -- smile. This is the cheerier candidate, presumably, the one with whom voters would prefer to have a beer.

In explaining the trajectory of presidential elections, U.S. history textbooks and professors don't sufficiently discuss the intuitive voter in American politics. In the last half-century, personality has seemed to dictate who ascends to the presidency more than any ideological pendulum.

If we study election-by-election, the candidate with the more authentic smile won. The first (and winning) candidate, listed in each match-up below, generally appeared happier along the campaign trail.

Obama vs. McCain: Obama emitted a cheerful charisma with which McCain could not compete. As then-Time magazine reporter Jay Carney noted during the general election campaign, McCain had lost his "sweet spot." His smiles and two-thumbs up mostly seemed contrived rather than genuine.

Bush vs. Kerry: While not the bubbliest candidate, and despite growing unpopularity, Bush appeared more upbeat and accessible in his facial expressions.

Bush vs. Gore: Likewise, voters found Bush to be less unemotional and more likely to crack a smile, compared to his more somber opponent.

Clinton vs. Dole: Once again, Clinton smiled more, which seemed far more fitting on his face than on the more aged WWII vet's.

Clinton vs. George H.W. Bush: The youthful former Arkansas governor pounced on the elder statesmen with many more "I feel your pain" empathetic smiles.

George H.W. Bush vs. Dukakis: Even the boring Bush scored more smiles than the stone-cold Massachusetts governor, who told debate watchers he would refuse the death penalty even in the hypothetical murder of his wife.

Reagan vs. Mondale: "I am not going to exploit for political purposes my opponent's youth and inexperience." Despite continued economic struggles, Reagan's characteristic humor and wit -- his constant charm -- brought about the ultimate demise of a less smiley career politician.

Reagan vs. Carter: Hollywood picturesque smiles overcame Georgia's sunny former governor, who had turned awfully serious.

The list continues with no obvious exceptions: Carter smiled more than Ford, Nixon more than McGovern and Humphrey, Johnson more than Goldwater, and Kennedy more than Nixon.

Some current political scientists, who believe central or forced-wedge issues dominate electoral results, would dispute the impact of voters' identity cues. They cite, most recently, gay marriage in 2004 or the new millennium's revival of "It's the economy, stupid" in 2008 (the stratagem executed in Clinton's successful '92 bid).

These front-and-center themes inevitably shape the context of presidential elections, be it 9/11 and its aftermath in 2004's re-election of President Bush or the financial meltdown that began on the cusp of Barack Obama's victory. And coherent and persuasive messaging is required for any victorious presidential campaign.