In a debate that moderator Charlie Gibson called “round 15 in a scheduled 10-rounder,” Barack Obama kept his guard up and Hillary Clinton pulled few punches.

The two remaining candidates for the Democratic presidential nomination debated at the National Constitution Center in Philadelphia Wednesday night as a prelude to the suddenly relevant Pennsylvania primary on April 22. The debate was intended to enable Pennsylvania voters to pick an opponent for John McCain in November, but it may only have proven that for all the talk of change, this election has not moved away from politics as usual.

After the latest fruitless attempt at getting the candidates to agree that whichever of the two lost would accept the role of running mate, moderators Gibson and George Stephanopoulos launched into questioning that would overpowered this debate. The moderators pressed Obama on his comments about bitter small-town Americans; lack of an American flag pin on his lapel; racial comments made by his former pastor, Reverend Jeremiah Wright; and his association with William Ayers, a former member of the Weather Underground, a revolutionary group that was responsible for politically motivated bombings in the 1960s and ‘70s.

As Obama tried to turn the debate to issues such as the Iraq war, health care and the economy, Gibson and Stephanopoulos applied pressure to controversial issues that have recently dominated the Democratic nomination process. Although Clinton’s comments about dodging sniper fire when she visited Bosnia were briefly discussed, the former first lady brushed it off with a joke and an apology, while Obama’s attempts to explain himself and disown the words of Wright and Ayers resulted only in more aggressive questioning.

“Wedge issues, hot-button issues, end up taking prominence in our politics,” Obama said. “And part of the problem is that when those issues are exploited, we never get to solve the issues that people really have to get some relief on, whether it’s health care or education or jobs.”

Clinton, calm and in control, repeatedly turned the spotlight back on her rival, implying that McCain’s campaign would have an easier time attacking Obama due to his controversies, but Obama retaliated. He criticized what he called a “game” in which the ideas of anyone he knows are attributed to him, and responded to Clinton’s concern about associating with Ayers and the Weather Underground by noting that President Bill Clinton pardoned two members of that organization during his time in office.

Once the moderators changed the topic from controversies to the more pertinent issues of the day, the candidates made it apparent why there has been so much focus on scandal and intrigue in the recent weeks of the campaign: the similarity of their platforms. Both candidates made note of their support for universal health care, although they were given no opportunity to elaborate on it, and both reiterated that they would begin withdrawing troops from Iraq within 60 days of being sworn in. They criticized President Bush over his handling of the war and painted McCain as someone who would only continue Bush’s Middle East policies – particularly taking cues on what to do in Iraq from General David Petraeus rather than deciding on his own.

“The bottom line for me is: We don’t know what will happen as we withdraw,” Clinton said. “We do know what will happen if we stay mired in Iraq. The Iraqi government will not accept responsibility for its own future. Our military will continue to be stretched thin. And our soldiers will be on their second, third, even their fourth deployment. And we will not be able to reassert our leadership and our moral authority in the world.”

Both candidates criticized Bush over what they viewed as a failed policy on dealing with Iran, and pledged to prevent Iran from acquiring nuclear weapons or attacking Israel.

“I would make it clear to the Iranians that an attack on Israel would incur massive retaliation from the United States,” Clinton said.

“My belief is that they should also know that I will take no options off the table when it comes to preventing them from using nuclear weapons or obtaining nuclear weapons,” Obama said. “And that would include any threats directed at Israel, or any of our allies.”

The candidates disagreed on how help stabilize Social Security. Obama was open to the idea of raising the cap on the payroll tax if he determined that the additional revenue would help. Clinton disagreed. She said Obama was willing to raise taxes on the middle-class, which both candidates promised not to do, and referenced the bipartisan commission created by Ronald Reagan and Tip O’Neill in 1983 as a way of finding a solution to Social Security then and now.

“I will say, number one: Don’t cut benefits on current beneficiaries,” Clinton said. “They’re already having a hard enough time. And number two: Do not impose additional tax burdens on middle-class families. There are lots of ways we can fix Social Security that don’t impose those burdens, and I will do that.”

Obama pointed out that Clinton seemed to neglect the results of the 1983 commission.

“That commission raised the retirement age, Charlie, and also raised the payroll tax,” Obama said. “And so Senator Clinton – she can’t have it both ways. You can’t come at me for proposing a solution that will save Social Security without burdening middle-income Americans and then suggest that somehow she’s got a magic solution.”

This debate was one of the rare occasions when the candidates discussed gun control, an issue close to the hearts of many Philadelphians due to the frequency of gun violence in their city. Clinton noted that there is one murder every day, on average in the city. Both candidates gave their support for the right to bear arms, as granted by the Constitution, but expressed support for solving the problem of gun violence at the local rather than federal level.

“There’s the reality of gun ownership and the tradition of gun ownership that’s passed on from generation to generation,” Obama said. “You know, when you listen to people who have hunted, and they talk about the fact that they went hunting with their fathers or their mothers, then that is something that is deeply important to them and, culturally, they care about deeply. But you also have the reality of what’s happening here in Philadelphia and what’s happening in Chicago.”

Clinton and Obama also touched on economic issues and made assertions of market manipulation and price gouging by gasoline companies and energy traders, and promised to investigate it and support a windfall profits tax.

Both candidates advocated affirmative action for people who are less privileged, regardless of their ethnic backgrounds, and Obama touched on creating more aid for college to replace high-interest student loans, but despite the 120,000 students in Philadelphia, the moderators did not ask any questions about higher education.

The candidates are next scheduled to debate April 27 in Raleigh, N.C., although Obama has not yet committed to the date.