By David Lauter

Fox News on Tuesday announced the lineup for the first Republican presidential debate, one that will probably be dominated by the figure standing at center stage, Donald Trump, whose attention-grabbing skills have allowed him to leap to the front of a crowded GOP field over the last six weeks.

Flanking Trump in the 10-candidate debate Thursday will be Jeb Bush, the former governor of Florida and onetime GOP front-runner, and Scott Walker, the governor of Wisconsin.

Sens. Marco Rubio of Florida, Ted Cruz of Texas and Rand Paul of Kentucky, former Arkansas Gov. Mike Huckabee, Govs. Chris Christie of New Jersey and John Kasich of Ohio and Ben Carson, a retired neurosurgeon, will round out the field.

The remaining seven announced GOP candidates will be invited to participate in a separate forum earlier in the day.

"Our field is the biggest and most diverse of any party in history, and I am glad to see that every one of those extremely qualified candidates will have the opportunity to participate on Thursday," Republican National Committee Chairman Reince Priebus said in a statement.

With 17 candidates who have announced that they're seeking the nomination, debate sponsors have to find some way to cull the field. Fox, the broadcast sponsor for Thursday's session, announced in the spring that 10 candidates would get to debate, picked based on who has the highest average standings in the five most recent national polls released by Tuesday evening.

Despite concern that the polls would vary widely, the most recent ones, including those released Tuesday morning by Bloomberg and CBS and Monday evening by Fox, all told pretty much the same story: Trump with a big lead, followed by Bush and Walker.

The main unanswered question over the last few days was who would be the odd man out among Kasich, Christie and former Texas Gov. Rick Perry. In the end, the polls made clear that the Texan would lose.

Whether by luck or smart tactics, Kasich announced his candidacy last month, just in time to be enjoying the usual announcement bounce in polls as the debaters get picked. The bounce is not much, but so far it has been enough to put him ahead of one or both of the others in most recent surveys.

In the Fox poll, Kasich had support of 3 percent of GOP voters, tied with Christie. Perry lagged behind at 1 percent. The poll, of 475 voters nationwide who said they were likely to vote in a Republican primary, has a margin of error of plus or minus 4 percentage points.

The Bloomberg poll was broadly similar, although it showed Christie, Cruz and Kasich all tied at 4 percent for the last three slots. Perry lagged behind at 2 percent in that survey. The poll, of 500 GOP voters nationwide, has a margin of error of plus or minus 4 percentage points.

The CBS poll differed at the bottom of the field, with Christie at 3 percent holding the ninth slot while Perry tied with Louisiana Gov. Bobby Jindal at 2 percent and Kasich had only 1 percent. It was conducted among 408 GOP primary voters and has a margin of error of plus or minus 5 percentage points.

In addition to the Bloomberg, CBS and Fox polls, Fox included polls by Monmouth University, located in New Jersey, and Quinnipiac University, which is in Connecticut.

Because the differences among the bottom candidates all fell within the margins of error of the polls, the exact order was largely a matter of random chance.

Fox News officials gave themselves considerable wiggle room on how to make the final decision. Although they had said they would average the most recent polls, they left some key details undefined until after the decision was announced. Afterward, network officials said they had used a simple, arithmetical average of poll results, rather than one weighted by sample size, and had rounded off percentages to the nearest tenth. Given that the candidates are tightly grouped together, those factors could all affect the outcome, but statisticians on the network's decision desk said there was at least a 90 percent probability that Kasich, in 10th place, was truly ahead of Perry, in 11th.

One point that all the polls agree on is that Trump continues to lead the field. He had support of 21 percent in Bloomberg's poll, which was conducted by J. Ann Selzer, an Iowa based pollster with a long track record of accurate polling, particularly in her home state. Bush was the first choice of 10 percent of those surveyed and Walker 8 percent.

In the CBS poll, Trump had 24 percent, with Bush at 13 percent and Walker at 10 percent.

Trump's support ranged broadly across subgroups within the GOP. Bush beat him barely among self-described moderates, the CBS and Bloomberg polls found, but he won among conservatives. He did less well with those earning over $100,000 and with evangelicals, the Bloomberg poll found.

(c)2015 Tribune Co.