Going negative in political ads, as Democratic presidential rivals Howard Dean (search) and Dick Gephardt (search) have done in recent days, is fraught with more risk in Iowa than New Hampshire, say political analysts.

Iowa has a long history of candidates refraining from mudslinging, while New Hampshire voters have seen their share of negative commercials, including skewering spots in 1996 when multimillionaire Steve Forbes (search) lit into Republican rivals Bob Dole, Lamar Alexander and Phil Gramm.

Linda Fowler, director of the Nelson A. Rockefeller Center of public policy at Dartmouth College in Hanover, N.H., said, "The difference is more than Iowans are nicer than New Hampshirites. It's more about turnout."

Fowler said that because New Hampshire, unlike Iowa, allows both Democrats as well as independents to vote in the primary, candidates are more willing to use negative advertising to reach the masses and court larger numbers of undecided voters, the group that typically is most swayed by attack ads.

"Until 1996, the norm here was you don't campaign using television ads and you don't run negative ads," Fowler said. "Forbes broke that taboo and succeeded in damaging Dole pretty badly and, in the end, Dole lost the primary here. Candidates saw that tactic worked."

Dean and Gephardt are in a close fight in Iowa, which holds its caucuses Jan. 19. Dean's once commanding lead in New Hampshire has shrunk as rival Wesley Clark (search), who is bypassing Iowa, has focused his attention on the state that holds its primary Jan. 27.

Dean started airing an ad in Iowa Tuesday that criticizes his rivals' support for the congressional resolution authorizing the war against Iraq. Gephardt began running a commercial in New Hampshire that highlights his opponents' support for trade deals he calls unfair. Both ads single out foes by name and in photographs.

Candidates use such ads to exploit their rivals' vulnerabilities, to influence undecided voters who don't know much about the candidates or aren't paying much attention to the race. But those who run such ads also risk turning off their own backers and, in a crowded race, having that support go elsewhere. The current Democratic field numbers nine.

In November, Dean's rivals scolded him, saying Iowa had a proud tradition of clean campaigns, after he ran an ad there that criticized Gephardt by name for helping to write the resolution that authorize war. Gephardt responded with a spot that accused Dean of flip-flopping on the issue of President Bush's request for $87 billion to rebuild Iraq and Afghanistan.

Until this week, those had been the only ads in which candidates criticized each other by name. A study the Wisconsin Advertising Project released Wednesday shows that candidates have run at least 21,000 ads in Iowa, spending at least $8.7 million there, compared to 7,500 spots run in New Hampshire at a cost of at least $6.5 million.

So far, Dean, Gephardt and long-shot candidate Dennis Kucinich are the only hopefuls running ads naming names. John Edwards, John Kerry, Joe Lieberman and Wesley Clark are running commercials that are positive, that go after Bush or that scold their opponents without naming them.

A random telephone survey of 400 Iowans for the Quad-City Times and KWQC-TV showed that 90 percent said they had seen at least one candidate ad in the state. Of that group, less than half said the ads would have some impact on who they would support.

Dennis Goldford, a political science professor at Drake University in Des Moines, Iowa, said the Dean and Gephardt ads are negative because they provide information that makes the voter uneasy about the candidate, but they are not vicious, and, therefore, likely would be forgiven by Iowa voters.

Plus, he said, Iowans likely would give a pass to such ads that talk about policy differences.

"Iowa tends to have fairly clean and wholesome political traditions. That's not to say there aren't negative ads because there are. People just don't tend to get nasty," he said. "This isn't Texas. This isn't Mississippi."

Determined to end his advertising campaign in Iowa on a positive note, Edwards includes a clip of his endorsement from the Des Moines Register, the state's largest newspaper. The North Carolina senator says in the ad, "I think that this is about something much bigger than these petty snipings that are going on. It's about a new, positive, uplifting vision for America — that's what we are about as Democrats."