Bruce Bartlett, one of the original supply-siders and a former member of both the Reagan and Bush 41 administrations, has written a feisty book, “Imposter: How George W. Bush Bankrupted America and Betrayed the Reagan Legacy,” that is climbing the best-seller list and getting a lot of attention.

There’s nothing quite so delicious in the eyes of much of the media as a conservative who turns on his own, and Bartlett does so with both barrels blazing. He likens Dubya to the hated Richard Nixon and even Herbert Hoover. He compares Bush’s political skills to those of Jimmy Carter. “On the Budget, Clinton Was Better,” is the heading of one chapter. It all fits very nicely with the left’s view of Bush as a lying, scheming, war-mongering, deficit-creating, Bible-thumping menace to the Republic’s very existence.

“What took you so long?” was the only question that foam-at-the-mouth New York Times columnist Paul Krugman could think to ask of Bartlett recently.

Now I count Bartlett as a friend and a mentor. I have nothing but contempt for the think tank that fired Bartlett because he broke ranks with Republicanism. And George W. Bush could do far worse than venture out of his presidential bubble to read this book for its often constructive criticism. But on the charge of “Imposter,” I have to say: case not proven.

Yes, Bush has done lots of un-conservative things (or more to Bartlett’s point, un-libertarian things), ranging from the woeful education bill cobbled together with Teddy Kennedy to his embrace of a make-the-world-safe-for-democracy foreign policy that would do Woodrow Wilson proud. It would have been nice if Bush had whacked Congress with at least one veto on spending. And no, Bush’s tax policies haven’t been Reaganomics at their purest.

But in the real world it’s hard to imagine which candidate with a realistic possibility of inhabiting the White House might have been more hospitable to conservative and libertarian ideas in domestic policy, which is Bartlett’s chief focus.

Bush did, after all, sign into law the capital gains and dividend tax cuts. He didn’t try to interfere with Alan Greenspan’s monetary management. And while he did raise steel tariffs briefly, he soon rolled them back. More recently he bluntly told the auto industry not to expect any protectionist help or bailouts – unlike the sainted Reagan, who forced “voluntary restraints” on Japanese car imports (with disastrous results).

Okay, conservatives have a fair point about the spending path. But “bankrupt?” The U.S. economy is powering towards a fourth year of expansion, and the bond markets – those gimlet-eyed judges of financial performance – are showing little sign of fiscal panic. Yes, there might come a day of reckoning, as Bartlett predicts, but economists have predicted at least 12 of the last three calamities.

Bush, meanwhile, has had the courage to open up the subject of genuine reform of Social Security (unlike Reagan, who settled for a big fat tax increase). He has so far managed to contain global warming hysteria, the left’s last best hope for sweeping government control over the economy. And he has delivered on his promise to place judicial conservatives on the courts, an achievement of surpassing importance to those – like Bartlett – who believe that the most important elements of a sound economy are the rule of law and solid property rights. (In fairness, Bartlett’s book appears to have been put to bed at a time when the Harriet Miers fiasco was still in full bloom.)

Bush isn’t perfect, as the cascade of recent political embarrassments from Katrina to the Dubai port issue underlines. But in politics, the real question is always “compared to what?”

Mr. Bray is a Detroit News columnist.