Hillary Clinton and Bernie Sanders will face off for the first time on stage Tuesday night, along with fellow Democratic candidates Lincoln Chafee, Martin O'Malley and Jim Webb. Both Clinton and Sanders have said they are running positive campaigns, but if their previous debate experience is any indication, that could change on debate night. In the past, both have shown a willingness to turn tough on their opponents. Here are seven moments we dug up from past debates that tell us more about what Clinton and Sanders will bring to the stage, plus one from Maryland Gov. Martin O'Malley: 1. Clinton is an experienced debater at the very highest level; there were 25 Democratic primary debates in 2008 campaign alone. And just like eight years ago, she is up against a candidate who is generating excitement and promising change. Here's how she handled the challenge from then-Sen. Barack Obama during an ABC News debate: "Making change is not about what you believe. It's not about a speech you make. It is about working hard. There are 7,000 kids in New Hampshire who have health care because I helped to create the children's health insurance program." 2. Clinton often struggled in those debates with Obama, with cheering crowds seemingly on his side. But not always. She said this, to cheers, in a CNN debate: "You know the hits I've taken in life are nothing compared to what goes on every single day in the lives of people across our country. And I resolved at a very young age that I've been blessed and that I was called by my faith and by my upbringing to do what I could to give others the same opportunities and blessings that I took for granted. That's what gets me up in the morning, that's what motivates me." 3. She also struggled back then with the word that's haunted her during this campaign, too — "likable." At a January 2008 debate in New Hampshire, she was asked by WMUR anchor Scott Spralding what she would say to voters who like her resume but are "hesitating on the likability issue," especially in comparison to Obama: Moderator: "My question you is simply this. What can you say to the voters of New Hampshire on this stage tonight who see your resume and like it but are hesitating on the likability issue. Where they seem to like Barack Obama more." Clinton: "Well that hurts my feelings [audience laughs]. Moderator: "I'm sorry senator, I'm sorry." Clinton: "But I'll try to go on. He's very likable. I agree with that. I don't think I'm that bad." Obama: "You're likable enough, Hillary. No doubt about it." Clinton: "I appreciate that." 4. Clinton has had to apologize in a past debate — which she will likely have to do again if and when she is asked about her use of a private email server during her time as secretary of state. An earlier controversy, her account of a trip to Bosnia, came up in an April 2008 debate in Philadelphia. She had said she landed there under sniper fire but later said she misspoke: "I just said some things that weren't in keeping with what I knew to be the case, what I'd written about in my book. And you know I'm embarrassed by it. I have apologized for it. I've said it was a mistake and it is, I hope, something that you can look over." 5. Clinton's chief rival this year, Bernie Sanders, has never been on a stage quite so big, nor has he faced an opponent quite like Clinton. Here he is in a 1998 debate, when he was an independent congressman running for re-election. It aired on Channel 3 in Burlington, Vt.: "The average Vermonter today is working longer hours for lower wages than was the case 20 years ago. What we have got to do is make the economy work for the middle class and working families, not just for the people on top." 6. Except for the eyeglasses people were wearing, you might not know whether that debate was yesterday or 17 years ago. Here he talks about increasing the minimum wage and trade policy: "I believe that in terms of the economy it's important to raise the minimum wage. Anybody that works 40 hours a week should not live in poverty. And we have got to change our absolutely failed trade policy." Sanders and Clinton are likely to clash on those very same issues during the debate. Clinton just came out against the Trans-Pacific Partnership trade deal — though she hedged her opposition slightly. Sanders has opposed it all along and has very publicly wondered how anyone could not know how they feel about it. On the minimum wage, Sanders wants it raised to $15 an hour. But Clinton has said $12 an hour for a national minimum wage might be easier to get through Congress. 7. In 2012, in a debate against Republican John McGovern on Vermont Public Radio, Sanders talked tax policy, with an edge: "You want to repeal the estate tax. Thirty-billion-dollar reduction in taxes for the wealthiest family in America worth $100 billion. And then you want to cut Social Security, Medicare and Medicaid. That, Mr. McGovern, is attacking people, the most vulnerable people in the country." 8. The big question around former Maryland Gov. Martin O'Malley is whether he will go after the front-runners. His poll numbers are largely nonexistent, and he has been agitating for more debates in part to boost his profile. His attack style has been much less aggressive than Clinton's or Sanders' — some might even say passive. In a 2010 gubernatorial debate, O'Malley was asked whether he would pledge not to raise taxes or significant fees. He answered by deriding opponent Robert Ehrlich for raising property taxes when he was governor "in easier times": Moderator: "He wants to know whether you will pledge not to raise taxes or significant fees in the coming years." O'Malley: "I'll tell you what I will pledge, I've never done that sort of irresponsible blanket pledge. But I will pledge not to raise property taxes like you raised property taxes, governor, when you were governor in easier times. I will pledge not to jack up college tuition by 40 percent. I will pledge not to increase by 300 percent the annual filing fee for every small business incorporated by Maryland. And I will pledge to not pretend that fees are not taxes."