Running for the Democratic nomination for president has taught John Edwards some things he did not know about American politics. And not all of what the North Carolina senator has learned is encouraging.

For instance, Edwards says, he has come to understand why campaigns so frequently turn so very ugly. As the candidate who many analysts see as the last contender with a chance to derail the juggernaut that is propelling Massachusetts Sen. John Kerry toward the party’s nomination, Edwards says he has come under intense pressure to attack the frontrunner.

“You can’t imagine the pressure to go negative,” says Edwards. “There are so many people who say, ‘This is what you have to do to win it.'”

In high-stakes contests, candidates do not merely get pressure from campaign consultants to savage their opponents in attack ads on television and take-no-prisoners mailings. The push to go negative can also come from prominent backers and financial contributors who want to make sure they are investing in a campaign that will go the distance.

Such prodding is usually felt behind-the-scenes. But, for Edwards, the pressure has moved out of the political backrooms and into the open.

In recent days, the first-term senator, who beat Kerry in South Carolina and has posted solid second-place finishes in caucuses and primaries elsewhere, has used an issues-based, populist campaign against corporate free-trade deals to battle his way into second place behind Kerry in polls of likely voters in tomorrow’s Wisconsin primary. With Kerry having already secured wins in fourteen of sixteen caucus and primary contests so far, many analysts say Wisconsin is a make-or-break state for Edwards and the candidate who is running third in most polls, former Vermont Gov. Howard Dean.

Yet, while Dean has attacked Kerry, Edwards has eschewed negative campaigning. That has helped him retain his “Mr. Nice Guy” reputation. And it has won endorsements from some prominent Democrats, such as Mayor Dave Cieslewicz, the progressive mayor of Madison, Wisconsin’s second-largest city. Cieslewicz said he was attracted to Edwards in part because of the senator’s clean campaign.

Yet, while everyone says they want campaigns to be upbeat, Edwards is taking hits for not hitting his opponents. A Sunday New York Times article on Edwards appeared beneath the headline, “Do You Need to Go Negative to Topple a Front-Runner?”

“Many Democratic strategists say that as he faces a critical primary in Wisconsin on Tuesday, it is time for Mr. Edwards to offer voters a reason they should not vote for Mr. Kerry,” noted the Times, above a quote form Democratic strategist Bill Carrick suggesting that a candidate in the position where the North Carolinian finds himself must launch “some substantial attack” in order to close the gap.

But Edwards shows no signs of ditching his resolutely positive appeal. In last night’s final debate before the primary, he would only go so far as to challenge suggestions that Kerry had essentially secured the nomination, exclaiming, “Not so fast, John Kerry.”

Political pundits like to say that the reason candidates go negative is because “negative works.” But Edwards does not think that is necessarily the case in presidential primaries.

“I don’t think that’s what voters want,” Edwards said in an interview before Sunday’s debate. “Voters want something bigger. They want a strong, optimistic vision for the country. They want to hear real ideas about what any of us would do as president, what I would do as president. I think it’s fine to point out differences to voters, for them to know what the policy differences are between me and Sen. Kerry. But that’s not really the thrust of what voters are looking for. They’re looking for someone who they think can be president, not someone who can run another candidate down.”

While the prodding to go negative is strong now, as state and national media speculates that a big Kerry win in Wisconsin could effectively end the competition, Edwards says it was actually worse before he surprised the pundits to beat out Dean and former House Minority Leader Dick Gephardt in Iowa. In Iowa, Kerry, Dean and Gephardt all took shots at one another. But Edwards stayed above — or, at least, outside — the fray. The North Carolinian had to struggle to stay out of the partisan bickering, however.

“The pressures were extraordinary back in late December and early January because I wasn’t moving then,” recalls Edwards. “I was way back in the polls, and everyone said, ‘You don’t have a chance. You better start attacking.’ But that didn’t ever feel right to me. I stayed true to what I believed, and it worked.”

Now, Edwards hopes that his refusal to attack other candidates may help him to secure the support of Wisconsinites who had been committed to Gephardt and another candidate who has left the race, retired Gen. Wesley Clark. And, though Dean remains in the running, Edwards thinks he could attract backers of the battered Vermonter.

“I’m more of an outsider. I have new, fresh ideas about how we change this country to make it work for everybody, so I think that my candidacy does have a lot of appeal for people who have supported Gov. Dean,” says Edwards.

Last week, in an interview with CBS News, Dean actually gave some encouragement to the Edwards candidacy. “I think that Sen. Kerry has an enormous advantage,” Dean said, referring to momentum Kerry has gained with each successive caucus and primary win. “My fear is that he won’t be the strongest Democratic candidate. I’ve actually said on the record that I think Sen. Edwards would be a stronger candidate against George Bush than Sen. Kerry because when Sen. Kerry’s record is examined by the public at a more leisurely time when we’re not having primaries every week, he’s going to turn out be just like George Bush.”

Even with an assist from Dean, Edwards would not attack his leading rival. But Edwards did note that he shared Dean’s view that he would be the stronger nominee.

The kind words from Dean regarding Edwards recall an incident in the 1992 Democratic primary for a Wisconsin US Senate seat. The frontrunners in that race, former US Rep. Jim Moody and businessman Joe Checota, attacked each other relentlessly. Things got so bitter that, in one of the last debates, Checota said Democrats who did not choose to vote for him should refrain from backing Moody and instead support a third candidate who had eschewed negative campaigning, Russ Feingold. Feingold won that primary and, in November, was elected to the Senate.

“I’m completely familiar with that race that put Russ Feingold in the Senate,” Edwards said on Sunday. “That’s part of what makes me know that staying positive can work in a Democratic primary in Wisconsin.”