Like all of the candidates in the Democratic presidential field, Sen. John Edwards (N.C.) has his share of weaknesses. But he remains, in some ways, the most interesting hopeful in the race — an articulate Southerner who is a sitting Senator but hasn’t spent his entire life in politics.

More than some of his opponents, Edwards has a straightforward, populist message that asserts he and his party “value work,” while President Bush “values wealth.” It’s a message that should appeal to core Democratic constituencies as well as to many middle-class and working-class voters.

And Edwards’ personal style should allow him to appeal to a wide range of voters, from various demographic categories and partisan perspectives.

But so far Edwards hasn’t caught on, and retired Gen. Wesley Clark’s entry into the race raises new doubts about the Senator’s ability to get traction.

Edwards has two glaring weaknesses that allegedly have derailed him before he got a chance to gain momentum in the contest.

First, his lack of foreign policy and national security expertise makes it difficult for him to talk about Iraq and terrorism. Edwards, his critics argue, hasn’t crossed the threshold of credibility on foreign policy matters, and given the Sept. 11, 2001, attacks and the war in Iraq, that eliminates him as a serious alternative for Democratic primary voters.

But wait a minute! Howard Dean isn’t exactly Dean Atcheson, and Vermont’s relationship with Canada and the rest of the world probably doesn’t qualify the former governor to discuss nuclear nonproliferation, international security arrangements or the Middle East.

Yet while Dean has little background in foreign policy and national security, he has successfully turned his criticism of Iraq into a credential that Edwards, Sen. John Kerry (Mass.) and Rep. Richard Gephardt (Mo.) can’t match. Dean is able to argue that he challenged the president’s foreign policy agenda, and that history has proved him right.

As it turns out, Edwards’ vote to authorize the use of force against Iraq is now a much greater problem for his presidential bid than is his lack of education, experience and expertise on international matters.

But I wonder whether Edwards’ bigger problem isn’t his youthful appearance and speaking style.

Yes, the Senator is 50 years old, and that makes him four years older than Bill Clinton was when elected president, and just four years younger than Bush was when he was elected in 2000. Edwards, however, doesn’t look 50. He probably could pass for 35.

The Tar Heel State Senator’s youthful appearance and speaking style (one observer I talked with argued that he often sounds bubbly and too eager, instead of authoritative) undoubtedly causes some primary voters to question his maturity and readiness for the nation’s top job.

Indeed, one Democratic consultant argues that Edwards’ biggest problem isn’t specifically his lack of foreign policy experience but a more general sense that he lacks the credentials and overall experience to handle the country’s top job at this time.

While Clark has never held office and Dean is running as an outsider, both men have a maturity and a level of accomplishment that this trial lawyer turned one-term politician lacks.

But Edwards has another problem that is not his own doing. “He’s snakebitten” is how one veteran of the political wars put it to me recently.

“At every turn, when it was Edwards’ chance to shine, there was a power outage. It wasn’t an outage on his part. It was a power outage on the stage,” added the campaign veteran, who pointed to the way Clark’s recent entry into the race stepped on Edwards’ announcement. “Every time that he had a chance to showcase himself, something happened.”

Another Democratic consultant put it a bit differently (and less sympathetically): “He’s in the wrong place at the wrong time. Good looks, wind-blown hair and standard comments on health care haven’t allowed him to distinguish himself.” In running a “conventional” campaign, the North Carolina Democrat never stood out from the crowd.

Edwards may have made a mistake by trying to run as a “fresh face” and as a Senator. In doing so, he allowed Dean to win the mantle of insurgent and political outsider but failed to become the consensus choice of the Democratic establishment. That made Edwards a man without a niche.

Of course, the clock has not yet run out on the senior Senator from North Carolina. At least one Democratic insider continues to refer to Edwards as “the ultimate second-look candidate” who could still benefit from a deeply divided Democratic Party and an extended fight for the nomination. But the Dean and Clark boomlets have clearly backed Edwards into an uncomfortable corner, forcing him to pull off a surprise somewhere.

Stuart Rothenberg is editor of the Rothenberg Political Report.