WASHINGTON - Donald Trump's rivals emerged from the second Republican debate newly confident that the brash billionaire will fade if the nomination fight takes a more substantive turn, and that they can play a role in taking him down without hurting their own White House ambitions.

That may be little more than wishful thinking in a race that so far has defied standard political logic.

"I keep looking for the speed bump that knocks Donald Trump off track," said tea party co-founder Mark Meckler. "I haven't seen it. We're in uncharted territory."

Trump may have had a lackluster performance in Wednesday's debate, but he's proved every prediction of his campaign's demise to be premature. Often, he's emerged from such moments with stronger support.

Even if Trump does falter in the coming weeks, several dozen Republicans interviewed by The Associated Press after the latest debate said no candidate is positioned to seize control if there's a void atop the unruly Republican field.

Jeb Bush cannot escape stubborn and strong skepticism from conservatives. On Friday night, the former Florida governor stuck by his support for the Common Core education standards, and drew boos from a crowd of thousands in South Carolina.

Scott Walker has been knocked from his top-tier status. For the Wisconsin governor, the campaign focus is squarely on Iowa. "Maybe not enough sizzle," said Daniel McCabe, a 65-year-old Republican from Stamford, Conn.

Former technology executive Carly Fiorina is emerging after a strong debate performance. But for now, she lacks the money and organization for the lengthy campaign most expect.

Trump's rivals say the debate, before a television audience of 23 million, did little to reshuffle the 16-candidate field. But they contend it was pivotal in exposing Trump's vulnerabilities, most notably his glaringly undeveloped policy positions.

"I have big problems with his lack of interest in learning about the job of being president of the United States," Bush said on Fox News. "This is a big, serious job and you have to have the skills necessary to lead."

With four more debates before the Iowa caucuses Feb. 1, the party's establishment wing is banking on Trump's policy gaps becoming more troublesome as the first voting nears.

Trump's rivals were also heartened by signs that the businessman known for his sharp barbs sometimes flinched when criticism came his way.

In post-debate calls with donors and other supporters, Bush advisers singled out his defense of his brother, former President George W. Bush, when Trump challenged his record. "You know what? As it relates to my brother, there's one thing I know for sure: he kept us safe," Bush said to cheers from the audience at the Ronald Reagan Presidential Library in California on Wednesday night.

After that exchange, Bush's team noted, Trump went silent for 37 straight minutes.

Fiorina, Bush and several other candidates followed the debate with appearances at Republican forums in South Carolina and Michigan. Trump had been scheduled to attend the South Carolina event, but pulled out Friday, citing a "significant business transaction."

Assessing the full impact of Trump's uneven debate performance will take time.

Polling is notoriously unreliable at this stage of a campaign and heavily influenced by name recognition. Because Trump is largely financing his own campaign, the whims of wealthy donors offer little insight into his standing with voters.

On Friday, Trump told The New York Times he was prepared to spend $100 million of his own money to win the nomination.

For other candidates, fundraising will consume much of their valuable time. They want to collect as much money as possible - a sign of political viability - before the latest reporting period ends Sept. 30.

Donors and fundraisers for most candidates are predicting a paltry showing, given that the reporting period covers the traditionally slow summer months - a time they say was further exacerbated by the puzzle of Trump's enduring prominence.

It's one at least some voters are ready for Republicans to solve.

"Republican primary voters are looking for somebody who will lower the size, scope, and cost of government and promote freedom, liberty and opportunity," said Mark Weyermuller, a 55-year-old Republican from Wilmette, Ill. "Hair is not an issue."