That would be a change not only from more doctrinaire liberals but also from the Bush administration, which has never been exactly obsessed with real-world data. If Obama were a true believer, he wouldn't care so much about evidence.

Boston College political scientist Alan Wolfe says, "Ideologues don't need that information, or want it, because they know what they want to do." Ask yourself: Is there any conceivable evidence that would cause George W. Bush to question the wisdom of tax cuts?

--He's not enchanted with the big-government model. On health care, Obama opposed Clinton's proposal to require every American to buy health insurance, preferring to offer subsidies and then let individuals decide. He balked when she said all adjustable mortgage rates should be frozen for five years -- with Obama's campaign quoting an expert who said, accurately, that it would be "disastrous."

He's far less suspicious of the operations of markets than most people in his party. And when was the last time a Democratic nominee openly worried about corporate tax burdens? Furman has said that if some loopholes can be closed, Obama "would like to cut the corporate tax rate."

Those who favor a less expensive and less expansive federal government will find plenty to complain about should Obama become president.

For consolation, they can try chanting this mantra: It could be worse.