(AP) -- The political veteran with the right resume, but perhaps the wrong last name. The rookie senators and their focus on foreign policy and individual rights. Governors with experience -- and baggage. The never-been-elected outsiders, and of course, the billionaire showman.

For the Republican Party, the narrowing of that vast field of presidential hopefuls begins in earnest Thursday with the first debate of the 2016 campaign. At stake for Republicans: not only picking the candidate to represent them in the general election, but also selecting the direction the party will take as it seeks to regain the White House.

"You're starting off with a lot of candidates who have an initial group of support that reflect a particular element of the party, but nobody is close at this point to putting together a majority coalition," said David Winston, a Republican pollster.

As in the 2012 Republican primaries, the GOP faces a tug of war between those eager for a candidate with broad general election appeal and those who think the key to winning is nominating a fiery conservative.

But this time, the field of 17 candidates is both larger and more seasoned, making the choice Republicans will ultimately make less certain or inevitable than in past elections.

While Republicans say they relish their options, it's doubtful many expected the summer surge of businessman and reality television star Donald Trump.

The real-estate mogul will stand at center stage during Thursday's prime-time debate in Cleveland, thanks to his status as the top performer in several recent national polls. Only 10 candidates were invited by debate host Fox News to participate in the main event, with the remaining seven relegated to a pre-debate forum.

With his unpredictable style and unformed policy positions, Trump doesn't fit neatly into any one segment of the Republican Party. That appears to be a draw to voters frustrated with Washington and career politicians, but some Republicans fear his talent for outlandish comments -- whether about Mexican immigrants or the war record of Arizona Sen. John McCain -- will taint the public's view of the party as a whole.

"A problem-solver that isn't a career politician is something that's appealing to many people," said Michigan Gov. Rick Snyder, a Republican. "But I would hope it could be done in the context of not being offensive to people."

Ahead of the debate, Trump said he doesn't plan to attack his rivals. "I'd rather just discuss the issues," he said Wednesday on ABC's "Good Morning America."

Standing to Trump's left on the debate stage will be former Florida Gov. Jeb Bush, a favorite of the wealthy donors and business leaders that populate the establishment wing of the Republican Party. But like Mitt Romney, who filled that role in 2012 before ultimately claiming the nomination, Bush has struggled to break away from the rest of the field.

The son and brother of former presidents, he also faces questions about whether his nomination would mark a return to the past.

To Trump's right on the stage will be Wisconsin Gov. Scott Walker, whose victories over unions in his home state created his national profile. Florida Sen. Marco Rubio, the youngest candidate in the field at age 44, is trying to carve out a niche as a foreign policy wonk, but has struggled to break through this summer -- particularly since Trump's surge.

A host of candidates with sharply conservative records and attention-grabbing personalities will seek to pull the party far to the right, including Texas Sen. Ted Cruz, surgeon and tea party favorite Ben Carson, and former Arkansas Gov. Mike Huckabee, a popular choice among evangelicals and social conservatives. Kentucky Sen. Rand Paul adds a libertarian twist to the Republican field.

Rounding out the top 10 are a pair of governors. New Jersey Gov. Chris Christie is a past favorite looking to return to the top tier, while Ohio Gov. John Kasich is a latecomer to the race whose first campaign for president 16 years ago never took off.

While the candidates pitch their visions for the Republican Party's future, they'll also be making the case that they would present the strongest general election challenge to Hillary Rodham Clinton, the frontrunner for the Democratic nomination.

Clinton was scheduled to be traveling during the debate and didn't plan to make a statement afterward. Her campaign was preemptively making the case that there was little difference between Trump's "outrageous" positions and the rest of the field.

"They all have an identical agenda," said Joel Benenson, Clinton's chief strategist.

Thursday's debate is the first of six Republican Party-sanctioned debates scheduled before primary voting begins in February. Fox News used five national polls to determine which 10 candidates would be on the stage, and several candidates were grouped together in the single digits -- most separated by a number smaller than the polls' margin of error.

Among those bounced to the earlier forum are former Texas Gov. Rick Perry and businesswoman Carly Fiorina, the only woman in the GOP field.

Undeterred by her B-squad status, Fiorina said she learned a long time ago not to be intimidated. She cited a male business colleague's decision to schedule a business meeting at a strip club when she was a young sales representative.

"I learned something, that I could and should stand up for myself," she said during an interview in Cleveland with Sirius XM Radio. "And he learned something, that she will stand up for herself."

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Associated Press writers John Flescher in Traverse City, Michigan, and Lisa Lerer in Washington contributed to this report.

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