Every Christmas morning is a shimmering promise of surprise and delight. You never know what it will bring, and you might just get your heart's fondest desire. But in reality, surprises are not the rule. If you want to know what you'll get this Christmas, your best guide is what you got last Christmas.
Likewise for presidential elections. Every campaign raises a host of possibilities, particularly in the imagination of candidates. They may be forgiven for ignoring all evidence that is unfavorable to their dreams, which is usually abundant. History suggests there are mysterious but inflexible constraints on the outcome of these contests.
We already know it's almost impossible to elect people from certain places - such as Massachusetts, which hasn't produced a president (or even a vice president) since John Kennedy in 1960. Edward M. Kennedy, Michael S. Dukakis and John Kerry might want to break the news to Mitt Romney.
Americans also don't elect candidates from New York, even though it has a horde of electoral votes. We used to find presidents there quite often, but not since 1944 has someone from the Empire State (Franklin D. Roosevelt) been elected.
That's bad news for Rudolph W. Giuliani, who has something else working against him: He used to be a mayor. Only two former mayors have ever reached the White House - Grover Cleveland and Calvin Coolidge. But they went on to serve as governors before seeking the presidency, a step Mr. Giuliani has skipped.
Hillary Rodham Clinton can take consolation that she's neither a mayor nor, really, a New Yorker. But history holds other ill tidings for her. Every morning, 100 senators see a future president in the bathroom mirror - and invariably it's a mirage. Americans rarely regard sitting senators as presidential timber. The last person to go directly from the Senate to the Oval Office was Mr. Kennedy, and prior to that, Warren G. Harding in 1920.
The good news for Mrs. Clinton is that if sitting senators can't win, she can stop worrying about Barack Obama, Joseph R. Biden Jr., Christopher J. Dodd and John McCain, all of whom are fated to turn into pumpkins. What about Fred Thompson? He's not a sitting senator, but the exclusion seems to apply to former ones as well (except those who become vice president).
Things are even tougher for House members, such as Ron Paul. His patron saint is James Garfield, the last congressman to jump straight to the presidency, back before the invention of the wheel. Bill Richardson has the distinct advantage of being a governor, like four of the last five presidents. But he has the misfortune of being a former Cabinet secretary, which is the political equivalent of concrete overshoes. No former Cabinet secretary has made the ascent to the Oval Office since Herbert Hoover in 1928.
John Edwards lacks that drawback, but he has the handicap of being a former senator, and he has created another for himself: He's running a populist campaign in a country where populists are all glitter and no gold. Every four years or so, someone emerges with a fiery pitch about helping the little guy and humbling the evil corporate interests. And every time, he's the one who gets a lesson in humility, from Fred R. Harris (1976) to Richard A. Gephardt (1988 and 2004) to Patrick J. Buchanan (1992 and 1996) to Al Gore (2000).
Recent history suggests that to win the presidency, you have to be a white male from the South or West, preferably with experience as a governor. That description fits only one candidate in the race - Mike Huckabee. So by examining the portents of history, we find that he's the only person who can possibly be elected.
Unless 2008 is one of those years that confirm what Henry Ford insisted: History is bunk.
Steve Chapman is a columnist for the Chicago Tribune. His column appears Mondays and Fridays in The Sun. His e-mail is firstname.lastname@example.org.