SIMI VALLEY, Calif. — The Republican field sparred for the title of anti-establishment champion Wednesday in the second debate of the presidential campaign, with front-runner Donald Trump defending his temperament amid attacks from fellow candidates, but struggling to lay out plans on how to deal with Syria or Russia.
Another nonpolitician, former Hewlett-Packard CEO Carly Fiorina, continued to gain ground, demonstrating how she won her way from the undercard debate last month in delivering a surgical attack on Mr. Trump’s knowledge while listing a host of steps she’d take to stiffen U.S. military resources in the Middle East.
Ms. Fiorina, Mr. Trump and retired neurosurgeon Ben Carson have surged in the polls of early primary and caucus states as GOP primary voters search for a candidate not tied to the Republicans who currently control Congress, and who have disappointed many conservatives by failing to halt more of President Obama’s agenda.
“If someone has been in the system their whole life, they don’t know how broken the system is,” Ms. Fiorina said. “A fish swims in water. It doesn’t know it is water. It is not that politicians are bad people, it is that they have been in that system forever.”
Mr. Trump took much of the fire in the early part of the debate, with debate moderator Jake Tapper of CNN asking the other candidates whether they would trust Mr. Trump as commander in chief. Ms. Fiorina wouldn’t take the bait, saying it was up to voters, but Sen. Rand Paul called Mr. Trump “sophomoric.”
“Do we want someone with the kind of character, with that kind of careless language to be negotiating with Putin?” Mr. Paul asked. “Do we want someone like that to be negotiating with Iran?”
Mr. Trump shot back, implying Mr. Paul was not an attractive person and didn’t deserve to be in the debate because he’s slid so far in the polls.
“Rand Paul shouldn’t even be on this stage. He’s number 11; he’s got 1 percent in the polls,” Mr. Trump said. “As far as temperament, I think I have a great temperament. What I am, far and away greater than an entertainer, is a businessman. That’s the kind of mindset this country needs to bring it back.”
The battle between establishment Republicans and the insurgents played out particularly over the issue of funding for Planned Parenthood, the nation’s largest abortion provider, which has come under fire after videos that show organization officials haggling over the price of fetal organs.
Ohio Gov. John Kasich said Mr. Obama wouldn’t sign a spending bill that defunds Planned Parenthood, so for Congress to insist on taking a stand is the equivalent of forcing a government shutdown for which the GOP will be blamed.
“When it comes to closing down the federal government, we have to be very careful about that,” he said.
Sen. Ted Cruz, the Texas Republican who has been pressuring party leaders in Washington to engage in the fight, said GOP leaders need to be as committed to their principles as Mr. Obama is, even if that means a showdown.
“We need to stop surrendering and start standing on principle,” Mr. Cruz said.
Ms. Fiorina said the videos are so disturbing that the GOP should force the fight and make Mr. Obama veto a spending bill over the issue.
She also brushed aside Mr. Trump’s recently reported comments mocking Mrs. Fiorina’s appearance, saying women across the country saw his remarks and are making their own judgments.
“I think she’s got a beautiful face, and I think she’s a beautiful woman,” Mr. Trump replied — as Ms. Fiorina stood stone-faced.
CNN structured the debate trying to elicit those sorts of conflicts, putting the candidates’ lecterns just 20 inches from each other.
Mr. Trump, however, mocked some of the decisions, including the three-hour time frame for the prime-time debate, accusing the network of “milking” it.
“Too long, too many people on stage,” he said, once again voicing a sentiment on the minds of many viewers.
Also in the debate were former Arkansas Gov. Mike Huckabee, New Jersey Gov. Chris Christie and Sen. Marco Rubio of Florida.
The 11 were selected and placed on the stage based on their standing in national polls dating back to July. CNN had originally intended to have only 10 but loosened the eligibility rules to put Ms. Fiorina on stage after posting an impressive performance in the undercard debate last month.
Mr. Trump was a target from the beginning of the debate.
“We don’t need an apprentice in the White House. We have one right now,” said Wisconsin Gov. Scott Walker, also taking a shot at President Obama.
And former Florida Gov. Jeb Bush, who saw his lead in the polls evaporate to Mr. Trump, repeatedly jabbed at the front-runner, including demanding that Mr. Trump apologize to his wife Columba, a Mexican immigrant, for mentioning her as the cause of Mr. Bush’s immigration views.
Mr. Trump complimented Mrs. Bush but refused to apologize, saying he had done nothing wrong.
Mr. Bush also denied Mr. Trump’s charge that he has been corrupted by campaign contributions, and said when he was governor of Florida, Mr. Trump was the only person who ever tried to buy him off in pushing to legalize gambling in Florida.
“Wrong,” Mr. Trump retorted — though he did compliment Mr. Bush, saying he had “more energy tonight. I like that.”
CNN hosted another undercard debate Wednesday ahead of the main event, featuring four lower-tier candidates: Sen. Lindsey Graham of South Carolina, former Sen. Rick Santorum of Pennsylvania, Louisiana Gov. Bobby Jindal and former New York Gov. George Pataki.
Mr. Graham delivered a series of zingers, including warning Republicans that unless they’re prepared to follow the example of former Sen. Strom Thurmond and have four children after the age of 67, they will have to be prepared to accept a new wave of immigrants.
But Mr. Graham, as the only one of the four in the early debate who is still serving in Washington, also took the brunt of the attacks aimed at the GOP establishment, with Mr. Jindal saying Mr. Graham and his colleagues have squandered the mandate voters gave them by failing to strip funding from Obamacare or Planned Parenthood.
“The one thing I am not going to do going into 2016 is shut the government down and taint our ability to win,” Mr. Graham replied. “What you are saying, and what Sen. Cruz is saying, I am really sick of hearing.”
⦁ Seth McLaughlin and Dave Boyer contributed to this article.