Republican front-runner Donald Trump has promised to implement a database to track Muslims in the United States.

Addressing reporters following a pair of town hall meetings here Thursday, Trump also noted that he had seen a bump in support after last week’s terrorist attacks in Paris. “People look at me as a strong leader,” he said. “The polls have been very much up since [the attack].”

The comments came after Trump told NBC News that he would implement a database to track Muslims. “I would certainly implement that. Absolutely,” he said. When asked whether Muslims would be legally required to register, he added, “they have to be—they have to be.”

During the town hall meetings, Trump defended his opposition to taking in new Syrian refugees—a shift from his stance in early September.

“We can’t take them,” he said. “It could be a Trojan horse.” Referring to video footage of refugees, Trump claimed that some refugees could seek to wage war against the U.S. from within, even though the U.S. government says only two percent of those admitted to the country have been males of fighting age. “They’re young men. They look like soldiers,” he said.

Trump maintained he was not being callous. “I don’t mind helping,” he said. “Let’s go to Syria and build a big safe area.” But he did not elaborate what a “big safe area” in the war torn country would look like, nor how he would create it. (Some of his GOP rivals have called for the U.S. to impose a no-fly-zone over parts of Syria to protect refugees.)

The pair of events were a marked change from the boisterous rallies Trump has held across the country in recent weeks. Trump arrived late to the first due to weather delays, he said. Both featured audiences of about 300 people—among his smallest events of the cycle—and attendees originally relegated to an overflow room were hastily shuffled into the main event to fill open seats.

“He’s used to large crowds,” said Trump Iowa co-chair Tana Goertz, a former contestant on his television show, The Apprentice, as she tried to hype up the crowd. “This is not our largest. But okay.”

Trump’s early remarks were focused on substantive issues like student loans and government subsidies. He said he was in favor of new government programs to assist student borrowers, backing refinancing and extensions for those in debt. Asked about wind energy, Trump said he believed the technology was impractical without government subsidies, which he added he was in favor of.

Trump also said he supported temporary work visas for agricultural workers “to make sure the grapes get picked”—a position apparently inconsistent with the immigration plan he has laid out on his campaign website.

When one woman asked him about childcare policies, Trump spotted a plant, asking the woman whether she had children—she didn’t—and then suggesting to the audience that he wouldn’t answer her question fully as a result. But he did say he provided childcare for the children of employees—called “Trumpeteers,” he said—adding that he thinks businesses, not government should step up. “It’s something that can be done I think very easily by a company,” he said.

Asked about equal pay laws, Trump said there was no role for the government in ensuring that men and women make the same for equal work. “People have to go out there and fight for themselves,” he said, after praising his daughter, Ivanka.

The usually-fiery candidate didn’t attack his rivals before the more sedate crowds at first, only doing so once an audience-member goaded him about Ben Carson, who briefly topped Trump in the polls in the Hawkeye State.

“I’m telling you folks, you’ve got a problem,” Trump said of Carson, accusing him of being “pathological” and puzzling over why Carson has been trying to convince voters he tried to stab somebody when a youth. “It’s a strange thing that’s happening,” he added, saying that Carson’s campaign was in “free-fall.”

Repeating his attacks from the past week, Trump also blasted Rubio for skipping hearings on ISIS to fundraising in California. “He’s missed more votes than anybody,” Trump said. “Yesterday, with what just happened in Paris, he’s out in California raising money…I think it’s outrageous.”

Trump warned that if any other rivals catch him in polls, “I’ll start doing a number on them.”

He also tried to make nice with the state of Iowa, after criticizing voters for boosting Carson in a long event in Fort Dodge last week. “I hate to leave Iowa,” he asked one woman. “Can I stay? Can I stay at your house?” He also promised that, should he win, he would uphold the state’s first-in-the-nation precedence in the nominating calendar.

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