Some pundits I know were doing pop-psych analysis on Eliot Spitzer the other day. Obvious risk-taker, they said, a player-with-fire who’d naturally patronize high-end prostitutes.

Sorry, I couldn’t see it coming. Hypothesize, though: Suppose the tangential mentions of Senator Obama in the trial of Chicago money man Tony Rezko turn into, well, something.

Saw it a mile away, people will say.

Yeah, sure. If they could, they’d ask why Democrats longing for a new kind of politics are about to nominate a guy from the old greased-up influence factory of Chicago.

Note that Mr. Obama so far is as pure as our still-unthawed snow once was. He has not been accused or even implicated of any crime.

Then again, Mr. Spitzer hasn’t been charged with anything either.

Mr. Obama, however, has been mentioned in the same breath as Mr. Rezko. Frequently. This is because some Chicago reporters embarrassed him with unanswerable questions. The national press noticed. Now, that press is no longer ignoring the Rezko trial, it’s studiously not paying attention except by alert peripheral vision.

Here is what we know. We know that Antoin “Tony” Rezko is on trial as the purported puppeteer of appointees to Illinois state boards with power over plums like whether hospitals can be built. We know that the governor of Illinois, Rod Blagojevich, once a fresh face with nice hair, had a patronage chief who consulted regularly with Mr. Rezko. We know Mr. Rezko raised a lot of money for Mr. Blagojevich — more than $1 million. We know that Mr. Blagojevich has much to fear.

We also know that Mr. Rezko raised a lot of money for Mr. Obama, about $150,000 to run for the U.S. Senate. We know that Mr. Rezko’s wife, of modest means, bought a lot at full price the same day the Obamas bought, from the same seller, a nice house next door at a discount in a costly neighborhood. Then the Rezkos sold a sixth of the lot to the Obamas, improving their yard and reducing the value of the Rezkos’ lot. It later emerged that Mr. Rezko toured the Obamas’ prospective home with Mr. Obama before the sale.

It was a “bonehead mistake” ever to be less than arm’s-length from Mr. Rezko, the senator now says. He sent back donations. He still won’t answer Chicago reporters’ questions about Mr. Rezko’s fundraising, though. Then there was the e-mail disinterred by Mr. Rezko’s lawyers this week that suggests Mr. Obama, among other officials, also consulted about appointees to the hospital board. Mr. Obama was then head of the Illinois Senate’s health committee, so this is natural. Yet there he was, mentioned in court again.

One must repeat that Mr. Obama is clean. Or as clean as his background permits. He’s a Chicago Democrat, so he’s had friends he’s had to denounce, such as Louis Farrakhan. He had a pastor who ran a theologically unusual black-power church. He is at least an acquaintance of two former Weather Underground fugitives now prominent in local leftist circles. All this and your quotidian Chicago political real estate deal, too.

None of this will likely sink Mr. Obama. We know that complicated real estate limburger can’t stink enough to destroy a popular Democrat. The Clintons taught us this. Their Whitewater affair sent friends and associates to prison, but as the floor collapsed, Hill and Bill managed to find footing.

Then again, sex scandals were private matters, as Bill Clinton showed, only this didn’t hold for Mr. Spitzer. So who knows?

My guess is that the Rezko trial will mean non-fatal but real damage for Mr. Obama in several ways.

First, it dims his halo. His appeal is a new kind of politics: Hope. Audacity. Yes, we can. Well, yes, he can work an audacious real estate deal with a purported political bagman. You can’t. Mr. Obama has the delegates, he’s probably got the believers, but this surely cools some of their ardor.

Second, the mention of his name near Mr. Rezko’s reduces his cynicism contrast with Mrs. Clinton. She’s been an operator since Day One, from handling bimbo eruptions to trading cattle futures to making a marriage of convenience with New York voters to achieve the Senate. The Rezko trial could make her baggage an asset: At least Democrats are pretty sure what her baggage is. With Mr. Obama, hints of revelation dribble out daily.

And most of all, the trial makes Mr. Obama look like an amateur. “Bonehead mistake” indeed: A lawyer so smart hanging out with a guy so unsavory — and so recently as 2005, when the home deal went down. Everything about Mr. Obama is recent, and the only place he’s been tested is the state where the most recent ex-governor was sent to the slammer and Mr. Obama’s last serious opponent imploded with a sex scandal of his own. Compared to Bill Clinton, notoriously fretting his political viability back in college, Mr. Obama seems to have traipsed along unaware of the open manholes along his path to glory.

To have such a candidate as its presumptive nominee is perhaps the fate of a party that draws its talent from Chicago — or Arkansas or New York. Talk about compulsive risk-taking: Scandals happen everywhere, but why did Democrats fall in love with a man from a town specializing in them?

Mr. McIlheran is a columnist for the Milwaukee Journal Sentinel.