As her once-formidable lead in national polls dwindles and Barack Obama moves ahead of her in the all-important Jan. 3 Iowa caucuses, Hillary Clinton will likely intensify her negative campaign against her rivals.

The Clintons' political MO has always had a good dose of negative campaigning, especially when the going gets rough. There's no reason to assume that they will alter their game plan now.

I remember Bill's race for re-election as Arkansas governor back in 1990, when he found himself falling behind Hal McCrae, his unknown Democratic primary opponent. After Clinton's 10 years as governor, McCrae's attacks - featuring Daliesque stretched-out clocks tolling the time for him to go - were hitting home. Hillary decided to attend McCrae's next press conference and engage him in a public, impromptu debate about his attacks on her husband. She gave as good as she got - and her foray marked the start of a four-week campaign of negative ads that brought McCrae down.

The Clintons used negative ads and attacks in each gubernatorial campaign - and, of course, in Bill's two races for president.

Until now, the '08 Democratic contest has been a referendum on Hillary: The basic decision facing voters has been: Would you vote for her? The Clintons need to get people thinking about whether they like her rivals any better.

Negative ads would do the trick - but at a price: By attacking an opponent, they'd concede that Hillary isn't inevitable. That would give Obama (or John Edwards, should they decide to aim at him instead) added credibility - and perhaps more access to funding and contributions.

Historically, such considerations have never deterred the Clintons - who are always ones to anticipate their adversaries' strength rather than to belittle it.

How will they do it? Continued...