Howard Dean (search) has up until now avoided serious attacks from his Democratic presidential primary opponents, but some campaign experts suggest the former Vermont governor may soon be in store for a political pounding.

If not, experts warn, the other nine Democratic presidential candidates will miss an opportunity to define themselves — especially now that newcomer Gen. Wesley Clark (search) has entered the race — and to keep Dean from racing even farther ahead from the pack.

“The Democrats are going to have to train their guns on him,” said Rich Galen (search), a Republican campaign strategist. “There’s an old saying I’m not sure they even use anymore: ‘It’s time to turn mother’s picture to the wall.'”

But other election experts say the time may have already passed for the candidates to take their best shots.

"In retrospect, they probably should have done this months ago," said Larry Sabato, director of the University of Virginia's Center for Politics (search). “Now they’ve missed their chance. He’s already climbed the mountain, he’s already the front-runner. Negative information today will have no impact."

In the latest polls, Dean is leading almost everywhere. In Iowa, he has topped Missouri Rep. Dick Gephardt (search), who needs the state to stay competitive. Massachusetts Sen. John Kerry (search) trails Dean by seven points in New Hampshire, which Kerry will need to win to have a shot at the nomination.

Some of Dean’s opponents have already cast the first stones. Since the first Democratic debate in New Mexico earlier this month, Dean has been forced to explain off-the-cuff remarks about the Israeli-Palestinian conflict and what have been described as “flip-flops” on issues like Medicare, Iraq, world trade, the death penalty and Social Security – all hot-button issues for the Democratic base that the primary candidates covet.

“I think all of the candidates are pointing out his misstatements, and his record,” said Dag Vega, a spokesman for Kerry’s campaign. “It’s out there.”

Vega said Kerry has hammered Dean recently on statements Dean made about the Palestinian terrorist group Hamas (search), calling them “soldiers” in the Israeli-Palestinian conflict. Middle-class tax cuts have been another point of contention between the two.

“We are very much interested in doing that, putting more into the clear differences between John Kerry and Howard Dean,” he added.

The Gephardt campaign has already rounded up a number of examples of Dean flip-flops and has put them on their Web site Deanfacts.com.

“Our campaign’s goal is not to rake anyone over the coals,” said Gephardt spokesman Eric Smith. “When Mr. Gephardt has legitimate policy differences with one of the candidates he will point them out. He’s been doing that all along.”

But the candidates are still a bit gun-shy when they share the stage with one another. Connecticut Sen. Joseph Lieberman (search) so far has come out strongest in recent volleys with Dean during the debates. He made headlines after a Sept. 9 Congressional Black Caucus Institute-sponsored debate by accusing Dean of touting a Middle East policy that appears to stray from decades of U.S. support for Israel.

Dean declined to comment for this story, but in recent campaign speeches has described changes in his points of view as a natural evolution of his ideology.

Friends of the Dean campaign added that the front-runner is prepared to handle whatever his rivals dish out. They say Dean handily dealt with Lieberman's accusations, and gently suggested that the senator save his attacks for President Bush.

“The way he handled Lieberman, he was very skillful, that was amazingly well done,” said Simon Rosenberg, director of the New Democrat Network (search), which has been helping out several candidates, including Dean.  “He disarmed his critic, that was a very effective move.”

Jim Pinkerton, Newsday columnist and Fox New Watch contributor, said he believes the clemency shown toward Dean so far is as attributable to external factors as it is to Dean's own strengths.

“It does surprise me a bit, but it does show how weak the field is, how much the press likes Dean and how little everyone thinks he’s going to win,” he said.

One of Dean's opponents in Vermont said that if they wanted to, Democrats could go on the attack over the former governor's record as head of the state he served for 11 years.

“They may be thinking why spend the money attacking him now, he might self-destruct,” said Ruth Dwyer, a former Republican state legislator in Vermont who ran unsuccessfully against Dean for governor in 1998 and 2000. “But it does surprise me a little that at least during the debates, they didn’t try to take him down. There’s certainly enough out there.”

Dean's primary opponents, along with the Republican Party, most likely have done a ton of "opposition research" already, Galen said, but the key is deciding when to go public with it. In politics, timing is everything.

“Just having this information isn’t enough. You have to know when best to use it,” he said, adding that that time "is getting close."

Galen said while it would require a bit of synchronicity, the best strategy would be to force Dean to deflect a number of different attacks by his opponents at the same time.

Republican pollster Kellyanne Conway agrees. She said she thinks the Democratic candidates need to get whatever they have on Dean out there now, and not be concerned that they will be perceived as callous or negative.

“If you leave it to others to do your dirty work it might not get done or it won’t get done the way it will benefit you,” she said.

Sabato speculated that Gephardt will save the big guns for the run-up to January's Iowa caucus, and Kerry will pull out more ammo right before the New Hampshire primary.

But whenever the gloves do come off, Dean will take the hits with finesse, Rosenberg said.

“His feistiness, and willingness to give a punch and take a punch, and comfort with the pressure from the other candidates is certainly not going to hurt him,” he said. “This is how it works. Governors are used to the back and forth.”