Here's who made the cut for Thursday's GOP debate

Billionaire businessman Donald Trump has made the cut for Thursday night's leadoff debate of the 2016 presidential race, joined by former Florida Gov. Jeb Bush, Wisconsin Gov. Scott Walker and seven other Republican contenders.

Seven others will be excluded, including former technology executive Carly Fiorina and former Texas Gov. Rick Perry, relegated to a pre-debate forum and second-tier status in the party's crowded field. Fox News announced the 10 Republican White House hopefuls who will take part in the debate.

Trump, after launching his campaign with a speech that labeled Mexican immigrants as "criminals" and "rapists," was initially thought to have no chance in the race, but the latest polls show him far outdistancing the top-tier mainstream Republican candidates. However, his negative numbers in the polls are also high and most observers remain skeptical about his chances of securing the nomination.

Beyond Trump, those selected among the top 10 – based on recent national polls – include 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. Making the cut could boost the chances of lesser-known candidates like Kasich.

The debate will be a key test for Trump. Some polls show his backing has grown to nearly double that of Bush, the brother and son of presidents.

Those who didn't make the field for the first debate include Fiorina, the party's only female presidential candidate, 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 announcement comes after the Republican Party that worked aggressively to improve its debates ahead of the election season. Yet with the largest field of contenders in modern memory, organizers say something had to give to ensure the debate in Cleveland didn't turn into a nationally televised circus.

"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 worked closely with TV executives, although the networks have the final say about which candidates will be allowed on stage for their televised events.

Fox News is the host of Thursday's event, the first of six party-sanctioned debatesbefore primary voting begins in February. The network says it used a selection of national polls to make this week's cut.

Republican officials were particularly concerned about Fiorina's status, hoping she would help balance Hillary Rodham Clinton's push to rally women to her candidacy. Trump's recent surge in the polls was particularly damaging to Fiorina.

The reality television star's rapid rise has surprised many Republican officials, some of whom fear his rhetoric on immigration and other divisive issues could hurt the party. In a Tuesday interview, Trump said he's been defying expectations all his life.

"I think people are tired, they're sick and tired of incompetent politicians," he said on MSNBC's "Morning Joe" when asked to explain his rise.

Fox didn't say before Tuesday's announcement which polls it would use to determine its top 10. Many candidates are 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.

Monmouth found that only five candidates – Trump, Bush, Walker, Cruz and Huckabee – were definitely in the top tier of candidates, while just two – Pataki and Gilmore – would not make it into the top 10 even when margin of error was taken into account.

All but three of the 17 Republican candidates for president participated in a New Hampshire forum Monday night that was essentially a "debate lite." Unlike Thursday's nationally televised debate in Cleveland, the gathering didn't have a cut-off for participation.

Without exception, the candidates aimed their criticism at Democrats instead of each other. Trump declined to participate and wasn't mentioned during the two-hour affair.