What does it take to win the White House? Books like The Keys to the White House have tried to answer this question since time immemorial, this one spelling out thirteen (count 'em, thirteen) keys to winning the Oval Office. Those of us who aren't academia nuts speculate on more pedestrian measures, like, "Who's taller?" Or the outcome of the last Redskins game before the election.

Most of these formulas try to predict the winning party, but Presidential elections are tests of will defined by individual leaders. What qualities do the winners of the last few elections share that the losers didn't? I think you can boil it down to five: executive experience, warmth, authenticity, electability, "the 14 year test," plus bonus points for incumbency or past national leadership. Get the most points and you have the most appealing general election candidate.

Here's a spoiler that doubles as full disclosure: I consult for a candidate, Rudy Giuliani, who comes out strong on these measures. But I'm utterly shocked by who else is near the top. Overall, the index does a decent job of explaining the appeal of the current field on both the Republican and Democrat sides. And the last three two-term Presidents -- Bush, Clinton, and Reagan -- scored 4 or more on this scale before being elected.

Executive experience. There's no disputing that the record of sitting U.S. Senators or Congressmen in seeking the White House is none too stellar. The last three two-term Presidents all hailed from executive offices. A direct promotion to the opposite side of Pennsylvania Avenue happened just twice in the 20th Century -- 1960 and 1920.

Score one for Rudy Giuliani and Mitt Romney; they've managed complex bureaucracies bigger than a Congressional office. A successful tenure at the head of a large organization is the job experience most directly applicable to the Presidency. Rudy Giuliani was a mayor, but for eight years was the leading political figure in a place larger than 39 states. Governor's mansions aren't the sole province of successful executives; Dwight D. Eisenhower managed a little thing called D-Day.

Warmth. This one is as close to an Iron Law of Presidential Politics as you can get: Warm beats cold. Bush beats Kerry and Gore, Clinton beats Dole and Bush, Bush beats Dukakis, Reagan beats Mondale and Carter -- they all fit the pattern. Since the advent of television, the candidate perceived as warmer and more approachable has never lost a general election. (The elections in the '60s and '70s that departed from this pattern were Cold vs. Cold elections.)

This election is an embarrassment of riches when it comes to extroversion and warmth. Count in Giuliani, Romney, Barack Obama, and John Edwards on this one. The jury is still out on John McCain, who was warm by virtue of his kinetic insurgency in 2000 but is running a different kind of campaign in 2008 (I'll grant him half a point because I'm a nice guy). The only one outside the Circle of Warmth is Hillary. As a candidate, she still has to prove that she would be more than an incremental improvement over calculating and technocratic Democratic nominees in the mold of Kerry, Gore, and Dukakis.

Authenticity. This represents a newer dimension in American politics, but one that was instrumental in both of President Bush's election victories. It was summed up by this line in Bush's convention address in 2004: "Even when we don't agree, at least you know what I believe and where I stand." Bush won those elections by being real and building a connection with Americans that transcended poll-tested 14-point policy prescriptions. Democrats have never adapted to this new model.

Authentic politicians speak more freely and are confident enough to acknowledge disagreements with the voters without pandering. Who has authenticity (or the perception thereof) on their side this time? Giuliani, McCain, and Obama.

Electability. This would seem like circular reasoning -- you can only be elected if you're electable. But if you have everything else going for and you're not seen as electable, the chances are you won't make it to the big show. John Kerry was nominated because of the perception that he was "electable." Potentially the biggest exception to this rule was Ronald Reagan, who trailed Jimmy Carter by 30 points or more in early 1980 ballot tests.

On this count, I see most of the major candidates on equal footing. Giuliani, McCain, Clinton, Obama, and Edwards can all be said to meet a basic threshold of electability, having led or been within the margin of error in most general election polls. The only one who consistently trails is Mitt Romney, and we wouldn't know until March 2008 (if he were the nominee) if this was because of his low name identification or something else. He doesn't get zeroed out just yet, but he does get docked half a point.

"The 14 Year Rule." In 2003, Jonathan Rauch posited the "14 year rule" -- the maximum amount of time it takes from when you're first elected to public office to a spot on a winning Presidential ticket. Call it a politician's "sell-by" date. It almost never goes wrong as a predictor of Presidential victory.

Kennedy, Reagan, and Clinton all were elected precisely 14 years after winning their first major office. Others like the current President Bush were even fresher; more experienced hands like Nixon and Bush 41 attained the Vice Presidency within the 14-year window. Romney, Obama, and Edwards are safely inside their sell-by dates. Rudy Giuliani (first elected in 1993) and Hillary Clinton fall right in a gray area -- Giuliani because municipal elections fall on odd-numbered years, Hillary because she has been a constant presence for 16 years, though she has been in elected office for eight. John McCain would nearly double the 14 Year Rule, with 26 years in Congress.

Bonus Points. Incumbents win most of the time, and people who wouldn't otherwise be considered Presidential frontrunners attain that status because of a little thing called the Vice Presidency. This year, we extend that definition to a former First Lady who is widely considered the Democratic frontrunner because of her past national prominence. She gets a half-point bonus. Why just half? Though past national leadership may get you into a general election, it traditionally hasn't trumped factors like executive experience in an open seat election.

The final score: Giuliani 4.5, Obama 4, Romney 3.5, Edwards 3, McCain 2.5, Clinton 2.5. How do past Presidential winners stack up? Bush arguably swept all 5, Clinton had 4 (minus authenticity), Reagan had 4 (minus electability). George H.W. Bush was arguably in the 2-3 range.

Though these may be dismissed as the ravings of a committed Giuliani supporter, I do believe this goes a long way towards explaining the current national momentum of both Giuliani and Obama. And yes, Obama's presence near the top of the list is surprising. Whether someone so inexperienced in public life can get elected hasn't been tested, but past experience shows that Americans may prefer fresher faces when it comes to the Presidency.

Am I wrong? And if so, how would you score both current and past candidates? Weigh in in the comments.