A piece I found on Politico written by Mark Penn….and he should know.

Clever negative advertising works. That is reality.

The tactic meets with media and pundit disapproval and spawns accusations of negativity, but the reality is that a clever negative ad can be devastatingly effective.

The 2008 presidential race is shaping up to be a close battle, and the tighter it is, the more the advertising will be ratcheted up, by both of the campaigns and the myriad independent groups sure to emerge.

Of course, voters publicly condemn negative advertising and suggest they would never be swayed by it. That was my experience in focus groups more than a decade ago, which found negative advertising to backfire. But Republican consultants such as the late Lee Atwater have used these tactics successfully in campaign after campaign. When reality and research differ, it is the research that is wrong.

Some negative ads crystallize voters’ opinions without presenting any new information. That’s what was behind John McCain’s recent ad equating Barack Obama’s celebrity status with that of Paris Hilton — that viewers would associate the Democrat’s leadership with mere celebrity, not substance. Fair or not, as advertising it did its job: It used humor, stuck viewers with memorable images and created a debate, just as Lyndon Johnson’s 1964 “Daisy” ad, Walter Mondale’s “Red Phone” spot 20 years later and Hillary Rodham Clinton’s “3 a.m.” commercial in 2008 did.
Other types of negative ads use candidates’ own words against them. During Bill Clinton’s 1996 campaign, we used to devastating effect the speeches that Republican nominee Bob Dole and House Speaker Newt Gingrich gave — especially a speech in which Gingrich admitted that his balanced budget plan aimed to cut off Medicare funds so the social insurance program would “wither on the vine.”

So far in the 2008 contest, neither candidate has connected with any ads that explosive. But fresh information about their past views in their own words could shake up the race.