NEWARK, N.J. » They have been holding mock debates, hunkering down with advisers and finessing policy answers. But the most pressing concern for many Republican presidential contenders as they prepare for the first debate of the 2016 primary season is one man: Donald Trump.

The billionaire businessman has dominated the 2016 Republican race in recent weeks, and he threatens to do the same when the top 10 Republican candidates — as determined by national polls — face each other for the first time on national television. It’s a high-risk, high-reward event for candidates eager to stand out in a packed field in which Trump is playing the ultimate wildcard.

"It’s the No. 1 unavoidability," said former House Speaker Newt Gingrich, a 2012 GOP candidate who had a knack for standing out in debates four years ago.

"Do not try to match him in anger and in aggressiveness. It’s not possible," Gingrich warned Trump’s rivals. "He’s a very instinctively aggressive guy and if you try to dance with him on his strengths he’ll run over you."

Indeed, despite his longshot status, the reality television star has commanded attention and seen his poll numbers rise after firing off provocative comments about immigrants, his presidential rivals and critics in both parties. His supporters love him because he’s willing to say what others only think. But that makes him dangerous in a debate setting, says Charlie Black, a leading GOP strategist who has worked on multiple presidential campaigns.

"Just try to ignore him," Black said. "The less attention you give him the better. I wouldn’t even look at him."

That’s easier said than done in a nationally televised program where Trump is sure to play a central role — literally, perhaps, if he’s positioned at the center of the stage as the leader in recent polls.

Count former Texas Gov. Rick Perry as among the candidates eager for a showdown, although he may not qualify for the Aug. 6 meeting in Cleveland. Only the top 10 candidates in national polling will be allowed on stage. With 16 declared candidates, several high-profile Republicans will be left out. Perry is on the bubble.

"If Donald Trump wants to sit on the stage and talk about solutions, I’m going to be happy to have that conversation," Perry said on Fox News. "But if all he’s going to do is throw invectives, then I’m going to push back and I’m going to push back hard."

Sen. Rand Paul of Kentucky told The Associated Press that he’s ready to be tested.

"You have to be able to stand your ground," Paul said, because politics is "somewhat of a body combat sport."

Even without Trump’s emergence, the first debate promises to be an unruly affair.

Never have more than 10 candidates taken the stage for a televised Republican presidential debate. Part of the problem is basic math.

In a 90-minute debate featuring so many candidates, there could be only enough time for four or five questions — with little time left over for the interaction between candidates that makes for an actual debate.

And few campaigns expect Trump to respect the time limits or other rules established by organizers.

Ron Kaufman, a senior adviser to 2012 nominee Mitt Romney who is supporting Jeb Bush, said Trump offers a prime opportunity to lesser-known candidates to get attention.

"I think they have to pick a fight with Trump," Kaufman said.

Many candidates have already been hard at work. Bush, one of the top contenders, recently brought in two veterans of Romney’s 2012 campaign, Beth Myers and Peter Flaherty, to help coach him. He says he hasn’t started intense preparation; aides say that will fill much of his schedule next week as he spends most of his time in Florida.

Bush has not participated in a debate as a candidate since his successful re-election campaign for governor in 2002.

"My objective with this is to, wherever I can, share my record," Bush said this week in South Carolina. "It’s one of accomplishment." He said he’ll go into the debate without thinking about Trump or any rival but that it’s his first presidential debate and he’s "not certain how all this plays out."

New Jersey Gov. Chris Christie specializes in wide-ranging and sometimes very long town hall meetings and recognizes he’ll need to be more focused in the high-stakes debate.

"You know, the big thing here with 10 people is going to be to make sure that your answers are tight and understandable," Christie said in New Hampshire. "It’s going to be about a discipline for me on how to most effectively communicate in a group of 10 people with a couple moderators in a short period of time."

Paul perhaps summed up the field’s feeling best when asked how he prepares to face someone like Trump: "Very carefully," he said.

Associated Press writers Bill Barrow and Meg Kinnard contributed to this report from Spartanburg and Bluffton, South Carolina.