The Republican Party might have challenges with outreach to Generation Z, but Nikki Haley, appearing in a Fox News town hall event on Sunday, said the answer was not TikTok, the Chinese-owned social media platform.

In a conversation with the “America Reports” co-anchor John Roberts, Ms. Haley, the former governor of South Carolina and United Nations ambassador, criticized President Biden for posting a TikTok clip on the night of the Super Bowl, in an appeal to younger voters. She also hit former President Donald J. Trump, her G.O.P. primary rival, for failing to curtail its use while he was in the White House.

“President Trump said he would ban TikTok, and when President Xi asked him not to, that fell to the wayside,” she said, referring to Xi Jinping, China’s leader. “We should have banned it from the beginning. It is incredibly dangerous.”

The volleys against both men are part of a broader argument Ms. Haley has been making in recent media appearances and on the campaign trail that it is time for fresh leadership. Her attacks on Mr. Trump, whom she served under as ambassador, have become sharper in particular, as the two head into a primary showdown in South Carolina on Saturday.

In the town hall event on Sunday, as she has before, Ms. Haley broke with the isolationist wing of her party on foreign policy and pummeled the former president for his friendly relationship with authoritarian leaders like Mr. Jinping and President Vladimir V. Putin of Russia. She argued that Mr. Putin “knows exactly what he did” with Aleksei A. Navalny, the outspoken Russian opposition leader who died last week in prison, and chastised Mr. Trump for suggesting he would encourage Russian aggression against U.S. allies in Europe.

“I think that’s why it’s so damaging when Trump said that he would choose Putin and actually encouraged to invade NATO allies, instead of standing with our allies,” she said.

When a young voter asked her thoughts on why she believed the G.O.P. had largely ignored Gen Z and first-time voters, Ms. Haley called it “a problem,” and argued that Republicans needed to do a better job of listening to a demographic with different concerns, like the environment and debt.

But asked her thoughts on the Biden White House and Democrats using TikTok for outreach, Ms. Haley renewed her calls for a ban, saying China had access to too much personal data.

“America can’t be the last country to ban TikTok,” she said.

TikTok became a political flashpoint as both Democrats and Republicans accused the app of not doing enough to protect the data of Americans. They also said TikTok downplayed its relationship with ByteDance, the parent company of the app based in China — where domestic laws allow the authorities in Beijing to secretly demand data from local companies. Senator Tom Cotton, Republican of Arkansas, grilled the chief executive of TikTok, Shou Zi Chew, during a hearing this month, insinuating that Mr. Chew was affiliated with the Chinese Communist Party, the country’s totalitarian ruling party.

Ms. Haley has taken those concerns to the campaign trail, calling for the app to be banned entirely. In a Republican debate in September, she called TikTok “one of the most dangerous social media assets” and attacked Vivek Ramaswamy, a rival candidate who supports using the app to reach young voters. The two continued to spar over the issue in the debates: Mr. Ramaswamy pointed out that Ms. Haley’s adult daughter uses the app. Ms. Haley called him “scum” in response.

She has called for a TikTok ban periodically on the campaign trail, accusing the Chinese government of using psychological warfare on American users by pushing content on the app that Ms. Haley deemed subversive. For example, in November, she argued that young Americans were more sympathetic to the Palestinian cause because of “pro-Hamas videos on TikTok.” Users had promoted the “Letter to America” — a text written by Osama bin Laden after the Sept. 11 terrorist attacks — on the platform in the opening days of Israel’s war in Gaza.

“You have members of our younger generation, they’re saying now they understand why he did it. That’s disgusting,” she said while campaigning in Iowa. “That’s not America doing that. That’s China doing that.”