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 -- like Massachusetts, which hasn't produced a president (or even a vice president) since John Kennedy in 1960. Ted Kennedy, Michael 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, including Chester Arthur, Grover Cleveland and both Roosevelts. But not since 1944 has someone from the Empire State (Franklin Roosevelt) been elected. The last New Yorker to make a plausible run for his party's nomination was Nelson Rockefeller in 1968, and he didn't come very close.

That's bad news for Rudy 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 both of them went on to serve as governors before seeking the presidency, a step Giuliani has skipped.

Hillary 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 Kennedy, and prior to that, Warren Harding in 1920. Kerry was nominated but lost, and dozens if not thousands of senators have foundered in Iowa or New Hampshire or some other primary state.

The good news for Clinton is that if sitting senators can't win, she can stop worrying about Barack Obama, Joe Biden, Chris 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). We have also never elected a comatose candidate, as Thompson appears to be.

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, and he didn't leave anyone yearning for more.

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 Harris (1976) to Dick Gephardt (1988 and 2004) to Pat Buchanan (1992 and 1996) to Al Gore (2000). Perhaps the premier populist in American history, William Jennings Bryan was also the premier loser -- nominated three times for president by the Democratic Party without ever winning.

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 next year.

Unless 2008 is one of those years that confirm what Henry Ford insisted: History is bunk.