Take a peek at the raw numbers, and it’s clear the left’s supposed "enthusiasm gap" is a canard; disillusioned liberals haven’t abandoned Obama en masse, much as his policies might warrant such an exodus.

Among those who describe themselves as "liberal Democrats," Obama still commands a stratospheric 83 percent approval rating, according to Gallup. Contrary to conventional wisdom, it’s moderate and conservative Democrats who have a bigger beef with Obama.

Obama’s presidency hasn’t been a complete failure (he can boast about student-loan legislation, the Lilly Ledbetter Act, and the stimulus, for example). But he’s performed abhorrently in many areas, kowtowing to Republican power plays, duplicitously filling his White House with former lobbyists, and continuing — and, at times, expanding — policies that flagellate the rule of law.

Obama appointed a non-educator to be his secretary of Education, a man who embraces many of the "school reform" movement’s nostrums. He didn’t push hard enough on climate-change legislation. He’s failed to end "Don’t Ask, Don’t Tell."

And earlier this week, in a characteristic move, Obama announced a deal with Republicans that would extend the Bush tax cuts for all tax brackets. (As he’s wont to do, Obama defended the deal with a little rhetorical realpolitik: "It’s not perfect, but …")

So will there be major political consequences for Obama’s tepid centrism? Or are progressives just being unfairly critical of Obama’s presidency? No and, for the most part, no.

Iowa could play a key role in answering the first question. An internecine fight would turn an otherwise boring Iowa caucuses into an exciting Democratic denouement. (That’s one of the reasons the press has eagerly advanced the story.)

But David Redlawsk, a former University of Iowa political-science associate professor and an expert on the Iowa caucuses, doesn’t see a challenge materializing.

"Any real challenger would already have to be out there building a campaign, and there is no evidence this is happening," he told me via e-mail. Redlawsk, who is now a political-science professor at Rutgers University, added, "There really isn’t any major Democrat who would take on Obama, at least not at the moment."

Sen. Russ Feingold, D-Wis., would be a great candidate, but he appears uninterested in running against Obama. Howard Dean, a less appealing candidate in my mind, has also said he won’t challenge the president.

That’s not to say Iowa progressives — and other civil libertarians — should just shut up and assent to Obama’s agenda. Many of his policies are objectionable and deserve strident criticism.

But those on the left should have regarded Obama as, at best, a palliative for a system of entrenched corruption. Single politicians, no matter their integrity, can do little to rectify a rotten political process.

As the late Howard Zinn wrote last year, "Where progress has been made, wherever any kind of injustice has been overturned, it’s been because people acted as citizens and not as politicians."

Those who thought otherwise were duped by Obama’s undeniably masterful campaign. His faux movement, however, sold a deified product that promised (fill-in-the-blank) change; marketers have been known to use faulty advertising.

As for the many liberal Democrats who still support Obama, I’d be wary of being a loyal apparatchik. He’s expanded our wars abroad, and his record on civil liberties has been abysmal. It’s not as if his administration has claimed the power to kill American citizens without due process because of Republican obstructionism.

Civil liberties issues aside, Obama shouldn’t provoke the vitriol he so often does. But he also deserves little praise. In the end, he’s just another politician.