Campaign debates can offer many ways to evaluate the candidates — and the 2008 presidential contest is certainly providing an ample array of face-offs where impressions might be gleaned. While pinning down the hopefuls on the issues gets most of the press attention at the debates, observing their onstage personalities also offers some clues about how they might behave as president.

Democrats kicked off the fall debate season last week in New Hampshire, while all the Republicans will meet in Michigan next week. Already, the two parties have staged a dozen of these showdowns between them and experimented with several formats.

With so many candidates competing for limited time, it is tough for any one of them to truly stand out in a single encounter. Over time, however, their character types emerge, telling us how they might market themselves in a general election campaign — and how they might come across in public if they became president. And among those top contenders who have been around since the debating began in the spring, a wide variety of personality types is becoming apparent.

• The Boss:Hillary Rodham Clinton has dominated her party’ s debates, displaying an unshakable confidence that has been much aided by the fact that her opponents tread so lightly on her. Rarely has the New York senator been forced to defend herself. In last week’s debate, when John Edwards challenged her support for keeping some combat troops in Iraq, Clinton finally felt compelled to interrupt in order to clarify her position on a major issue. Besides that moment, she’s never had to betray her sense of calm with an interjection — mainly because her rivals have mostly deferred to her as if they know she will be the nominee and they must stay in her good graces.

• The Student: For all of his charisma on the campaign trail, Barack Obama comes across like an unsure student who memorized a few lines from the textbook to recite when the teacher asks a tough question. The Illinois senator’s failure to stand out in these sessions or make any direct effort to shake loose Clinton’s front-runner status is eroding his position as the main alternative to her. Still, his deep baritone voice and knack for inspirational phrases could sustain him as the most presidential-appearing Democrat — if he can do a better job of the give-and-take in debates.

• The Advocate: John Edwards is so polished and passionate that he is often compared unfavorably to the slick style of an evangelical minister. But many Democratic voters like his telegenic looks and willingness to show a bit of fervor for the plight of the poor and the middle class. And lately the former North Carolina senator (and millionaire trial lawyer) is presenting a tough debating style as the only rival with the fortitude to directly take on Clinton, producing a back-and-forth with her in last week’s debate that put her on the defensive. Look for Edwards to dramatically step up the pressure on Clinton in future debates.

• The Tough Guy: Rudy Giuliani comes across as the street-smart crime fighter he was when taking on the mob as a federal prosecutor before becoming mayor of New York. He delights debate audiences with lightning-fast zingers aimed at Democrats. Giuliani keeps this edge on when challenged about his liberal views on social issues, considered his main liability among conservative Republican primary voters. He doesn’t back down from his stands and so far seems to have persuaded many social conservatives to overlook their differences with him and focus on his tough, partisan side.

• The Chairman: Mitt Romney looks and behaves like the corporate elitist he was before becoming governor of Massachusetts, somewhat disengaged from the details but always ready with a pat response. Watching him in debates, you can imagine Romney presiding over a board of directors meeting with great ease — so long as everything goes according to script. He seems flustered, however, when fielding the inevitable oddball question which presents no obvious answer that he can pluck from his briefing book.

• The Rebel: John McCain shifted personalities during the course of the debates as his campaign organization and fundraising fell apart. He did not seem comfortable as the above-it-all front-runner, the role he tried to play in early debates. Now, the Arizona senator is back to playing the role that won him so many fans in his 2000 presidential bid: Luke Skywalker, the feisty young pilot who battled the galactic empire in “Star Wars.” The question is which character he would be as president — the maneuvering politician of his early debates or the bomb thrower seen in his latest performances?

Fred Thompson is the only major contender not yet tested on a debate stage, heightening interest for his first appearance at next week’s GOP forum. Based on the former Tennessee senator’s public persona (and his acting roles), look for him to be the gruff, but avuncular, stalwart of traditional conservatism — one of the few roles not yet cast in the 2008 race.

Contributing Editor Craig Crawford is a news analyst for NBC, MSNBC and CNBC. He can be reached at ccrawford@cq.com.