It didn’t take long. Within hours after this year’s voting had ended, at least four presidential aspirants – Republicans John McCain, Rudy Giuliani and Duncan Hunter, and Democrat Tom Vilsack – took steps to run in 2008.

And just as quickly, the handicappers started rating the candidates – Obama’s up, Kerry’s down, Allen’s dead. We’ve decided to avoid that game (for now) and offer five rules for evaluating the vast field of White House wannabes that are already bidding for attention and money.

HISTORY MATTERS. Only two presidents – Warren Harding and John Kennedy – were sitting senators on the day they were elected. Since Kennedy’s victory in 1960, at least 40 lawmakers have tried and failed to win the White House, and this is not an accident. Americans like candidates with roots outside of Washington. Four of the last five presidents have been governors, a sure sign that it’s easier to run from Plains, Ga. (Carter) or even Beverly Hills (Reagan) than from Capitol Hill.

Long-standing lawmakers cast a lot of votes that are hard to ignore or defend. And they cannot control their own schedule or agenda. Congressional business often pulls them back to Washington from the campaign trail to consider issues they’d rather not talk about.