Why does it seem that Republican columnists have better sources among Democrats than everyone else?

Here's John Fund, writing in today's OpinionJournal.com:

The murmured charge is that as an Illinois state senator, Mr. Obama engaged in a real estate deal that benefited him in exchange for legislative favors. In short, what might pass for standard operating procedure in the Illinois legislature could nonetheless prove embarrassing to someone campaigning as a paragon of political virtue for president. So far, however, no proof of the allegation has been presented.

Pretty thin stuff. And haven't we heard the Tony Rezko tale already?

For the record, the Obama and Clinton campaigns try to plant negative stories about each other all the time. Felonious fundraisers, issue positions, legislative records, the occasional guilt-by-association catches -- those are fair game.

Other stuff seems to be off-limits.

Earlier this year, Obama donor David Geffen mouthed off to Maureen Dowd about the verbotten subject of the Clintons' private life, triggering an intense bout of jockeying between the Clinton and Obama campaigns. Then -- silence.

Except for the isolated occurrance -- an Obama aide plopped down next to me at a campaign event and wondered when reporters would begin to look into Clinton's postpresidential sex life - not a single rumor about the subject has eminated from the Obama world.

Some aides been gotten dressed down for talking about the subject, even in private, with other campaign staffers.

Likewise, no one in the Clinton universe has ever tried to convince me to look into something scandalous about Obama's past -- all the bad stuff -- cocaine use, hard-knuckle Chicago political tactics -- is out there already.

One caveat: "The Clinton Universe" is so big that there are bound to be free agents operating without sanction. When one of those advisers, for example, made fun of John McCain's experience in a Vietnamese prison cell last year, Hillary Clinton, and not McCain, was embarassed and forced to apologize on behalf of someone who claimed to be close to her.

Past scandals have been generated by campaigns. Who tipped off reporters to allegations of Gary Hart's indelity? To Joe Biden's plagiarism of a British politician's speech?

But these days, with the profusion of voices and outlets, rumors don't need official channels to spread, and often, campaigns caught spreading them risk the ultimate penalty.

So if campaigns don't traffic in these rumors, who does?

Supporters do -- it's true that reporters in Iowa and New Hampshire are accosted by Democrats who don't like Hillary Clinton and wonder why the press doesn't ask her about her husband's fidelity.

Donors do -- think of Gossip Girl set in a Georgetown salon.

Opposition parties do -- everyone tends to assume that negative stuff against Hillary Clinton is being sent around by her Democratic opponents. Not always true.

And reporters do -- we can't help it.