By Sarah Ewall-Wice, CBS News–

The Democratic presidential primary debates begin this week, with the first contest taking place over two nights, with ten candidates each night and five moderators. And right now, each candidate is trying to figure out how to use his or her precious few minutes of speaking time to stand out in the crowd.

A moment that people remember

“What will matter most in these initial debates is to have a moment,” says Bob Shrum, director of the Center for the Political Future at USC Dornsife and top adviser on both John Kerry’s and Al Gore’s presidential campaigns. “A moment that people remember. A moment where you crystallize what your candidacy is about. A moment where you somehow push off against the field in a way that benefits you.”

The primary advantage of the debates is that they’ll give candidates the opportunity to challenge their opponents face-to-face. This kind of confrontation often results in the kind of “moment” Shrum is talking about. It can be especially important for lower-ranked candidates taking on the front-runners.

“If you can get into an actual debate over something with [Biden or Sanders], or some of the other candidates that are getting more press coverage, you’re more likely to get in the paper and in the replay on television, so people are definitely thinking about that,” said Karen Dunn, who led debate prep for President Obama’s re-election.

Strategists agree that this is where Warren, the highest-ranking candidate on the first night, could face a disadvantage. On Wednesday night, Warren will be debating along with Bill de Blasio, Tim Ryan, Julián Castro, Cory Booker, Beto O’Rourke, Amy Klobuchar, Tulsi Gabbard, Jay Inslee and John Delaney. So it’ll be more difficult for her — or anyone on that stage — to effectively criticize front-runners Joe Biden and Bernie Sanders, who won’t be standing next to them or even debating on the same night.

a screen shot of a person: Campaign 2016 Debate© David Goldman / AP Campaign 2016 DebateOn Thursday night, Biden and Sanders will be on stage with Marianne Williamson, John Hickenlooper, Andrew Yang, Pete Buttigieg, Kamala Harris, Kirsten Gillibrand, Michael Bennet and Eric Swalwell.

Candidate prep

Some of the candidates have been open about what they hope to accomplish in the debates Wednesday and Thursday. Biden, as the front-runner, isn’t focused so much on his opponents going into round one.

“I am preparing,” the former vice president told CBS News during a trip to Iowa earlier this month. “Basically, I’m looking at less about what the other people are for or against and trying to figure out how I can get to the place where I can communicate to the American people what I believe, why I’m running, and why it’s important.”

a large white building with White House in the background:    The 2020 presidential election is more than a year away, but   many hopefuls are already announcing their candidacies.       While many potential Democratic candidates have yet to   announce their intentions, some have already launched   presidential campaigns, including Massachusetts Senator Elizabeth   Warren and Maryland Representative John Delaney.       Here's a list of the major party 2020 presidential   candidates.

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O’Rourke, a former Texas congressman, says that his time on the trail is what’s training him for Wednesday night. “You’re seeing me prepare right here. Listen to people, answering their questions. Gaining the benefit of their ideas in every community that we visit,” O’Rourke said earlier this month in South Carolina.

Many of the candidates have done their share of town hall events, fielding unscripted questions from voters in the early-voting stages. But until now, they haven’t had to prepare for facing off on a crowded stage.

“Do you line up nine of your aides and say let’s practice ten people on stage?” CBS News’ Ed O’Keefe asked Harris, a California senator, over the weekend in South Carolina. “Well, I think we will do that,” she replied. “We haven’t yet… but you know, I will be, I’ll be working on it; that’s for sure.”

And then there’s the time crunch, the red lights and the chime that’ll tell them their time to talk is up. “I’m trying to learn to talk in just one-minute segments,” laughed Sen. Warren, of Massachusetts, over the weekend. “And that’s hard.”

Confrontation

Not all of the candidates have waited for debate day to start taking aim at the competition. Sanders, independent senator of Vermont has already slapped at Biden on the campaign trail, pointing out his past votes to approve trade deals and the war in Iraq. Harris has criticized Biden’s recent comments about working with segregationists.

Sanders isn’t immune from attack either. Hickenlooper has lambasted Sanders over socialism.  Now, all four will be sharing the debate stage on Thursday.

And then there is the Trump factor. While the president won’t physically be on the debate stages, his presence looms.

“I do think what Vice President Biden has done in attacking the president is a smart move for him  because he probably can’t win a primary where he’s just talking about Democratic orthodoxy,” said Republican strategist Brett O’Donnell who helped prepare Governor Mitt Romney for presidential primary debates. “He won’t pass that test.”

For other candidates, O’Donnell says the options are not as clear-cut. “There is this big choice that a lot of the candidates have to make and that is, if I’m on the debate stage with Joe Biden, do I need to attack him because I’m thinking about winning the primary, or do I try to sell myself as the person who can defeat President Trump and hope that will sell voters on me?”

Buttigieg, the mayor of South Bend, seems to be thinking about calibration. It is a competition, he recently pointed out, but at the end of the primary season, there can only be one Democratic nominee.

“We have got to remember that at the end of the day, we’re all on the same team, and we all have to support, the 22 people who don’t become the nominee have to support the one who does, and everything we do now should reflect that,” he said.

In the end, whatever the strategy, in the primaries, it all comes back to having that moment. “A successful debate for any one of these candidates leads with coverage of a moment that they are in, and they are successful in.”