Republican presidential candidate Carly Fiorina went after the only other woman running for president during Fox Business Network's undercard debate on Jan. 14. (Sarah Parnass/The Washington Post)

The Republican “undercard” debate Thursday night concluded with all three long-shot candidates promising that they’d be the best to take on the Democratic front-runner — glossing over, for the moment, the seven other Republicans they’d have to beat first.

“You cannot wait to see the debate between me and Hillary Clinton. You would pay to see that fight,” said former tech executive Carly Fiorina, casting herself as a stand-in for women everywhere.

“Citizens, it is time,” Fiorina said. “We must take our country back.”

The other two low-polling candidates on the stage — former senator Rick Santorum (Pa.) and former Arkansas governor Mike Huckabee — talked about races they had run against Clinton’s allies. “You want a fighter? You want a winner? I’d appreciate your vote,” Santorum said.

The tone of Thursday night’s early Fox Business Network debate in North Charleston, S.C., was unusually fearful and confrontational, as all three candidates onstage hoped for a Hail Mary — a single breakthrough moment that would elevate them to the top tier of candidates. One candidate raised the prospect of a nuclear doomsday; another brought up the prospect of the government taking people’s guns.

Mike Huckabee, Carly Fiorina and Rick Santorum participate in Thursday’s undercard debate. (Scott Olson/Getty Images)

If nothing else, at least they were there, debating publicly for an hour prior to the seven-candidate main debate later in the night. In his closing statement, Santorum mocked Sen. Rand Paul (R-Ky.), who failed to qualify for the main debate stage and then declined to show up for the undercard debate as being beneath him.

“I’m going to take some of Rand Paul’s time here for a second,” Santorum said after his own speaking time had run out.

Earlier in the evening, Santorum had sought to reframe a plan to deport illegal immigrants as a “gift” from the United States to both the immigrants and their home countries, bringing the benefit of U.S.-educated and U.S.-assimilated people.

“I’m going to give them the gift of being able to help the country they were born in. We’re gonna export America,” Santorum said when asked about his plans to increase deportations of people who entered the country illegally. “They can start a renaissance in their country so they won’t be coming here anymore!” he said to loud applause.

For Huckabee, the plan was to allege conspiracies by President Obama to crack down on gun owners and seize firearms from lawful owners. Huckabee was cheered when he said he would encouraged gun sellers to disobey Obama’s latest executive actions that expanded background checks for gun sales.

Huckabee said he wasn’t sure that Obama could be trusted to leave guns in their owners’ hands.

“If you like your gun, you can keep it, too,” Huckabee said, paraphrasing an unkept promise by the president that all Americans could keep the health insurance they had after his health-care bill passed. “Frankly, we don’t buy it. He’s lost his credibility.”

Santorum raised fears of an apocalyptic attack by Iran, which he said would develop a nuclear weapon because of Obama’s efforts to sign a nuclear deal. Santorum said that Iran was not like other countries, and that it might use the weapon to hasten a doomsday for religious purposes. An “electromagnetic pulse” attack, involving a nuclear weapon detonated in the upper atmosphere, could shut down all electronics in the United States, Santorum said, repeating some of his deeply worried messaging from the campaign trail.

Huckabee also offered skepticism about the U.S. military effort in Afghanistan, saying that he saw little hope for rebuilding a nation “like the land of the Flintstones.”

“It’s been that way for thousands of years,” Huckabee said of Afghanistan, although parts of that country were relatively modern before the long and destructive fighting that began with the Soviet invasion of Afghanistan in 1979.

All three candidates said Obama was too passive and permissive in foreign policy, and all promised more aggressive ­stances toward rivals such as Iran and Russia, as well as the Islamic State.

Fiorina was asked whether, in an effort to fight the Islamic State, she would accept an alliance with Russia and Iran. She said no, and added that the United States must stick by Saudi Arabia in its ongoing tensions with Iran.

“Saudi Arabia is our ally, and Iran is our adversary,” Fiorina said after offering a list of Middle Eastern allies whose leaders she knew personally. “Vladimir Putin and Russia are our adversary. We cannot outsource leadership in the Middle East to Iran and Russia.”

Fiorina was also skeptical of Obama’s latest efforts to expand background checks for gun buyers. So was the audience: When a Fox moderator noted that polls show widespread support for expanded background checks, the crowd booed.

“Not in this room,” Santorum said.

That’s what the polls show, the moderators replied.

“And we all believe the poll data all the time, don’t we?” Fiorina said.

Jose A. DelReal in Iowa and Sean Sullivan and Ed O’Keefe in Washington contributed to this report.