Sen. Barack Obama and John Edwards sharpened their attacks on Democratic presidential frontrunner Sen. Hillary Clinton Tuesday, taking swipes at her character and use of “textbook” political strategies that they say prove she'll say anything to get elected.

“She defends lobbyists and she defends the system. So she is status quo, and I think we have to bring about change, so I think there's a significant difference between her and me on that issue,” Edwards said after a town hall meeting at a local high school in Durham, N.H.

The Clinton team “parses and calculates and shifts for political position," Obama senior adviser David Axelrod said on the Today Show Tuesday. "That is textbook politics, and they are very good at it.”

Clinton, who's leading by 26-plus points in nationally averaged polls, is not taking the attacks broadside. Since the recent shift of aggression toward her, the New York senator has amplified the intra-party criticism and attempted to turn it back on her opponents.

She has put some of the stories about the negative campaigning on her Web site. A memo circulated by Clinton strategist Mark Penn also claims Obama and Edwards have abandoned the high road.

“Considering that both Senators Obama and Edwards made their names by pledging to be positive, the last thing one would have expected was for either of them to go out and announce with pride that they were now going to go negative on a fellow Democrat. It’s unprecedented in my experience,” the memo said.

The sniping plays prelude to the Democratic debate Tuesday night at Philadelphia's Drexel University. It’s the first debate in a month for the seven scheduled Democratic participants. During that hiatus, Clinton has solidified her position as the frontrunner, gaining in polls, taking the lead in fundraising and dominating the agenda.

That has only hardened the attacks by Clinton's opponents. On Tuesday, Edwards suggested Clinton is part of a corrupt system in Washington.

"I believe the system in Washington is broken that it doesn't work; that corruption has seeped into that system; that people like the lobbyists in Washington have far too much influence on what happens there; and I believe that system has got to be cleansed of that corruption, and made to work for America in order to solve the country's problems. Senator Clinton feels differently," he said.

The argument marks a shift in a race where Edwards' and Clinton's other Democratic opponents have criticized her stance on policy but usually have avoided taking on her character directly.

A recent poll by CNN shows Clinton may be vulnerable on the issue of honesty and integrity. While a majority of voters surveyed see Clinton as a strong and decisive leader, likable and caring about their needs, voters were split roughly in half when asked whether she is honest and trustworthy; whether she shares their values; and whether she is a person they admire.

Edwards has been focusing his criticism almost entirely on Clinton, ignoring the threat from Obama even though all three are within striking distance of each other in polls of Iowa caucus-goers, who will vote Jan. 3. Edwards said that is because he and the Illinois senator often are on the same page, although they disagree on some matters.

They appear to agree on their distrust of Clinton.

Obama has recently criticized Clinton for her vote on Iran and for failing to explain how she would save Social Security. Sources at the Obama campaign said they have no plans to respond to the Clinton memo sent out Tuesday and are "100 percent" focused on the debate, acknowledging that expectations are high.

Observing the infighting apparently from afar, candidate Bill Richardson said Tuesday he regrets the "negative tone" that Obama and Edwards have taken in trying to portray Clinton as beholden to special interests.

Richardson predicted he will win the nomination in part because he is running a positive campaign.

Richardson, Clinton, Edwards, Obama, Delaware Sen. Joseph Biden, Connecticut Sen. Christopher Dodd and Ohio Rep. Dennis Kucinich are set to participate in the debate.

FOX News' Carl Cameron and Serafin Gomez and The Associated Press, contributed to this report.