HANOVER -- As Democrats gather at Dartmouth College for the third of six DNC-sponsored debates, a dominant story line of the campaign so far is coming to a close. Like the unwelcome coming of fall, many decried the early start of the primary season. For candidates trailing in money or in polls, the refrain was similar: It's still early. There's plenty of time left to catch up.

With just over three months and just one fundraising quarter left before ballots are cast, tonight's debate marks the beginning of game time. If second-tier candidates don't break out within a very short period of time, they will find themselves little more than footnotes in history.

For two top candidates, the risk of being left behind is also becoming clear in a way it hasn't before. Senator Hillary Clinton, a recent University of New Hampshire/CNN/WMUR poll shows, is solidifying her lead, and now enjoys the support of more than twice as many Democrats as her nearest rival, Senator Barack Obama. Obama and former Senator John Edwards, searching for holes in Clinton's armor, will use tonight to launch more vollies her way.

If they fail, and if Clinton maintains an ever-widening aura of inevitability, Obama and Edwards will find themselves with one fewer chance. Those chances are dwindling fast. And while fans of both will point out, rightly, that 55% of respondents said they were still trying to decide on a candidate, Clinton's lead will be hard to overcome. Even if many are still unwilling to commit, they are leaning toward the New York Senator. Attacks launched tonight will be aimed at dislodging those tentative masses.

The second tier will not allow the debate to become a focus on the trio of front-runners. Each will fire their own salvos, attempt to distinguish themselves in some way and do whatever they can to make it into tomorrow's stories.

Clinton, the undisputed leader of the pack, has much riding on the debate, but if her previous appearances are indicative, she can further stand above the pack. Obama likely has more at stake tonight, as many pundits are beginning to question whether he is anything more than the second-place finisher. But whoever wins tonight, in the eyes of the media and the viewing public, will have scored a point in a contest with increasingly few opportunities to do so.