CLEVELAND - Ten candidates have made the cut for the first Republican presidential debate today, with polling front-runner Donald Trump hoping for a civil evening but ready to pounce if attacked.

The seven others lagging in the polls and relegated to an afternoon forum? Call them the not-ready-for-prime-time players, at least in the eyes of debate organizers.

Sharing the Cleveland stage with the billionaire businessman will be former Florida Gov. Jeb Bush, Wisconsin Gov. Scott Walker, Texas Sen. Ted Cruz, Kentucky Sen. Rand Paul, Florida Sen. Marco Rubio, retired neurosurgeon Ben Carson, former Arkansas Gov. Mike Huckabee, New Jersey Gov. Chris Christie and Ohio Gov. John Kasich.

Candidates with time to watch that debate are former tech executive Carly Fiorina, former Texas Gov. Rick Perry, Louisiana Gov. Bobby Jindal, South Carolina Sen. Lindsey Graham, former Pennsylvania Sen. Rick Santorum, former New York Gov. George Pataki and former Virginia Gov. Jim Gilmore.

The largest field of contenders in modern memory challenged debate organizers. Fox News relied on an average of five national polls to decide the lineups for the prime-time debate and the forum four hours earlier.

"We never ever envisioned we'd have 17 major candidates," said Steve Duprey, New Hampshire's representative to the Republican National Committee who helped craft the debate plan. "There's no perfect solution."

Republican officials were particularly concerned about Fiorina's status, hoping she would help balance Democratic front-runner Hillary Rodham Clinton's push to rally women. Trump's recent surge in the polls, a surprise to many Republican officials, damaged Fiorina's chances.

Some Republicans fear that Trump's rhetoric on immigration and other issues could hurt the party.

"I probably am the target," he said Wednesday on ABC's "Good Morning America." He said he did not want to attack any of his rivals and preferred to "just discuss the issues" in the course of a "very civil" debate. Still, he made clear that if attacked, he would have "to do something back."

Trump was far and away the front-runner in the five most recent national polls that determined the debate lineup. Several candidates were grouped together in the single digits, most separated by a number smaller than the margin of error.

For example, in a Monmouth University survey released Monday, Kasich was the 10th candidate with the support of 3.2 percent of voters. But after taking the margin of error into account, Monmouth noted that Kasich's support could be as low as 1.5 percent, while almost any of the candidates who polled lower could be that high or higher.

Five more party-sanctioned debates are scheduled before primary voting begins in February.

"This first debate is just one opportunity of many," Amy Frederick, an aide to Fiorina, wrote supporters. "With many more debates to come, we fully expect that Carly will soon stand on the stage and show America what real leadership looks like."

Jindal spokeswoman Shannon Dirmann issued a challenge of sorts: "The governor will debate anyone anywhere at any time."

Candidates already began to turn their attention toward Trump.

Asked about Trump while courting religious conservatives on Tuesday, Bush said the businessman's rhetoric on immigrants is "wrong." ''We have a different tone and a different view," he said.

"I respect the fact that he's the front-runner for the Republican nomination," Bush continued. "This is a serious thing. But I think to win and govern the right way - we have to unite rather than divide."

If you watch

• The first GOP primary debate will take place today at 6 p.m. PST on Fox News.