Vice President Lai Ching-te of Taiwan rose to prominence as a pugnacious opponent of Beijing’s claims over the island. But now, as a leading candidate in Taiwan’s presidential race, he is likely to present a more muted persona when he visits the United States starting Saturday. Expect restraint, not rousing speeches, Taiwanese officials and scholars say.

Nonetheless, his stops in New York and San Francisco will be closely watched — in Taiwan, in Beijing and in Washington — for clues to how he might handle crucial relations with the United States and China as president, a top issue in Taiwan’s intense presidential race. And his visit, however low-key, is also likely to prompt an escalation of Chinese military flights and naval maneuvers near Taiwan, bringing into focus the risks of real conflict over its future.

“Even without such special political events, there’s actually been quite a high level of harassment of Taiwan by People’s Liberation Army planes this year,” said Shu Hsiao-huang, a researcher at Taiwan’s Institute for National Defense and Security Research, a government-funded body in Taipei. “The People’s Liberation Army would never let a major foreign policy event like this slip by.”

Mr. Lai, 63, a former doctor who uses the name William, emerged from a wing of his Democratic Progressive Party that has pressed Taiwan’s aspirations for fully exercising sovereignty, and he has previously called himself a “pragmatic worker for Taiwanese independence.”

But as Mr. Lai vies to succeed President Tsai Ing-wen, who has a determinedly buttoned-down manner, he is also seeking to assure Taiwanese voters, and probably Washington, that he can be a steady pair of hands. In a brief statement at the airport before leaving, Mr. Lai said he would use his visit to Paraguay — one of only 13 states that retains formal diplomatic relations with Taiwan — to promote his island democracy’s global role, and he mentioned his brief stay in New York only in passing.

His visit, he said, would “let the international community know that Taiwan is a country that upholds democracy, freedom and human rights, and also let the international community know about all our efforts to maintain peace and stability in the Indo-Pacific.”

Beijing regards Taiwan as Chinese territory, and as its military strength has grown, so have fears that it could try to impose unification by force. Taiwan’s partnership with Washington has become central to deterring that possibility. Most Taiwanese voters desire neither unification nor open conflict with China, and the Biden administration also says that it wants to maintain the current ambiguous status quo, with no surprise shifts by Beijing or by Taipei.

“Lai wants to reassure the United States and its allies,” said Lu Yeh-Chung, a professor of diplomacy at National Chengchi University in Taipei. “He wants everyone to know that he is not a troublemaker.”

Mr. Lai has no plans for major speeches or meetings with prominent members of Congress, said two Taiwanese officials close to Mr. Lai. (Meetings with senior members of U.S. presidential administrations do not happen even for Taiwanese presidents.) Both officials spoke on condition of anonymity to describe the internal plans. Mr. Lai will meet members of the Taiwanese-American community and give remarks at a dinner in New York, and a similar community event is likely to take place in San Francisco, one said.

Though the United States severed formal diplomatic ties with Taiwan in 1979, it lets its leaders make transit visits. Mr. Lai’s travel plans reflect the more modest protocol that comes with being a vice president, said the Taiwanese officials. But that lower key also fit with Mr. Lai’s political goals, they said.

“He travels to the U.S. as a presidential candidate to send a message that he is ready,” said Sung Cheng-en, a scholar of international law at the Taiwan New Constitution Foundation, a think tank that is aligned with Mr. Lai’s ruling party. “He wants to convey a message that he is stable and reliable, whether that’s during the election campaign or for his international role.”

But the Chinese government is likely to seize on Mr. Lai’s trip to stage a show of military force near Taiwan, several experts said. Beijing is trying to curtail Taiwan’s international contacts, and Chinese leaders nurse a special loathing for the Democratic Progressive Party, which seeks to assert Taiwan’s separateness from China, a position that Beijing says is tantamount to seeking outright independence.

After Nancy Pelosi, then the speaker of the United States House of Representatives, visited Taiwan last August, China’s military held a week of exercises around the island. China also held days of exercises in April after Ms. Tsai visited the United States on her way to and from Latin America, and met the current Speaker, Kevin McCarthy, in California.

Competing factors will weigh on how intense Chinese retaliation is this time. Beijing hopes that Mr. Lai’s party loses the presidential election in January, and has long leaned to the Nationalist Party, which favors expanded contacts with China. Menacing exercises around Taiwan could hurt Nationalist chances by provoking a backlash among voters.

But Xi Jinping, China’s top leader, is unlikely to let Mr. Lai’s stopovers go unnoticed and risk being seen as weak. Chinese military flights near Taiwan have increased markedly since Ms. Pelosi’s visit. Beijing has already issued a stream of denunciations of Mr. Lai’s trip. Chinese maritime authorities also announced that starting on Saturday three days of military exercises would be held in seas more than 300 miles north of Taiwan.

“We warn the Democratic Progressive Party authorities that there is no way out for ‘Taiwan independence,’ and fawning on the United States and selling out Taiwan is a disaster for the Taiwanese people,” the Taiwanese affairs office of the Chinese Communist Party said about the visit.

Mr. Lai will spend Sunday in New York, and then fly to Paraguay to attend the inauguration of president-elect Santiago Peña, according to a schedule issued by the Taiwanese government. En route back to Taiwan, Mr. Lai will spend an evening and part of a day in San Francisco.

Mr. Lai has sought to douse anxieties that he would pursue drastic changes in Taiwan’s status if elected. He has said that his comments about being a “pragmatic worker for Taiwanese independence” just meant that he wanted to more fully exercise Taiwan’s current sovereignty.

Yet he has also sought to promote his government’s ties with the United States as an election asset, while accusing his opponents of gullibility about China. They reject that characterization and argue that Mr. Lai would be a risky choice.

“This election is a choice between Zhongnanhai and the White House,” Mr. Lai told supporters last month, referring to the Chinese Communist Party headquarters in Beijing. “When we can go to the White House — when the Taiwanese president can enter the White House — we’ll have reached the political goal that we’re pursuing.”

His comments prompted requests for clarification from U.S. officials, the Financial Times reported.

Mr. Lai is so far leading most polls. He is competing against Ko Wen-je, former mayor of Taipei, who is heading an insurgent campaign drawing on discontent with the established parties, and Hou Yu-ih, the candidate for the Nationalists, who so far has lagged in most polls.

“There is some trepidation about the pending change in Taiwan’s leadership,” said Bonnie S. Glaser, who is an expert on Taiwan and managing director of the Indo-Pacific program for the German Marshall Fund. “While the U.S. will work with whoever is elected president, the transition is fraught with uncertainty and risk, whichever candidate wins.”