WASHINGTON -- David Axelrod, the seasoned Chicago Democratic political operative who is chief strategist for Sen. Barack Obama's presidential campaign, was taken by surprise in the last minute of CBS's "Face the Nation" on Dec. 2. Howard Wolfson, Sen. Hillary Clinton's spokesman, accused Obama of running a "slush fund." In fact, the Clinton campaign was spreading that story privately months ago.

Last summer, a senior Clinton aide told a famous Democratic personage believed favorable to Obama that the Illinois senator was using his "leadership" political-action committee to spread money around the country to grease his presidential prospects. That message was private when Clinton seemed far ahead for the Democratic nomination. It became public when Obama threatened to overtake her.

Before Wolfson spoke out, one of Clinton's close supporters was spreading the word of unspecified defects in Obama that should deter Democrats from supporting him for president. This is the Clinton style that has proved effective for two decades, but Obama has continued to close the gap. This attack mode works best when the accusations are hidden from public view.

Last summer, a few Clinton insiders -- headed by her Senate chief of staff, Tamera Luzzatto -- paid a presumably social visit to the Cape Cod, Mass., vacation home of a prestigious Democrat reported to be in Obama's corner. Luzzatto warned that Obama was ethically challenged because of his leadership PAC. My sources indicated that this was not an isolated incident, and the slush-fund story was spread widely.

In a later incident, a Democrat, not on Clinton's Senate or campaign staffs but close to her, a month ago approached a party activist who has not made a commitment with this message: Skeletons in Obama's closet would make him vulnerable if nominated. He did not elaborate and said the Clinton campaign would keep its anti-Obama information to itself, remembering mutually destructive assaults between Howard Dean and Dick Gephardt in 2004 that enabled John Kerry's nomination.

The Clinton campaign denied all this, claiming a Republican plot. In truth, I have not talked to a single Republican in my reporting of attacks on Obama. In the wake of these denials, Wolfson made public his slush-fund accusation on "Face the Nation," shortly after polls showed Obama passing Clinton for Iowa's Jan. 3 caucuses:

"There's a lot that voters don't know about Barack Obama," said Wolfson, "and one thing that they don't know we found this week, which is that he has been using and operating a so-called leadership PAC in apparent contravention of campaign-finance laws." Wolfson demanded that Axelrod say whether he would "shut down Sen. Obama's slush fund." With only 20 seconds left, Axelrod's answer sounded lame: "I think it is shut down, Howard. I don't know that there's any money left in it."

With more time, Axelrod might have noted that Obama's PAC contributed to Clinton's 2006 New York re-election and in the current cycle to Jeanne Shaheen's Senate campaign in New Hampshire though her husband, Bill Shaheen, heads that state's Clinton campaign. The slush fund just did not measure up to claims of dark improprieties by Obama, and the Clinton campaign did not pursue the issue after volleys were exchanged between the candidates.

The attack strategy has not affected Obama, and Clinton's aura of inevitability fades. Not only has she fallen behind in Iowa's Jan. 3 caucuses, but polls show subsequent primaries in New Hampshire and South Carolina are too close to call. Howard Dean was in a much stronger position in post-Iowa primaries in 2004 than Clinton is today, when his third-place finish in Iowa was followed by his national collapse.

The use of the phrase "slush fund" in American politics is hoary, dating back to a $5 million appropriation in 1874 administered by the federal Treasury, according to "Safire's New Political Dictionary." In 1952, contributions to a slush fund for the use of vice presidential candidate Richard M. Nixon nearly forced him off the Republican ticket. When Hillary Clinton started slipping two weeks ago, her campaign responded by unlimbering the Obama slush fund. The fact that this bomb proved pretty much a dud raises doubt about the whispers of impropriety by this untried new candidate.