But it was the sentiment expressed by Mr. Chen during the rally that suggests why, unless Beijing resorts to force, the China-Taiwan divorce could be permanent. Polls show that the generation of islanders who identify as “Chinese” is fading, and more people are identifying themselves as “Taiwanese.” Decades of de facto independence have whetted Taiwanese appetites for the real thing. Polls show most Taiwanese are unwilling to rejoin even a democratic China.

These feelings will deepen as a younger generation of Taiwanese finds its political voice. Indigenous identity and attachment to liberal civic values are strongest among the increasingly assertive youth, whose Sunflower Movement spawned the New Power Party, which in coalition with Ms. Tsai’s Democratic Progressive Party toppled several Kuomintang incumbents in the election.

Still, while Taiwanese may increasingly identify with a unique local culture — and the passion of someone like Mr. Chen — for now they prefer Ms. Tsai’s more measured public persona. A cerebral technocrat, she is different from the earthier elders in her party, some of whom started their political careers in Kuomintang prisons.

Even as Ms. Tsai’s surrogates played the identity card, her campaign stressed economic competence and promised no formal independence, a position meant to avoid offending Beijing and Washington. Yet Ms. Tsai’s party platform still advocates independence, and her victory will give her power to entrench Taiwan’s separateness with subtle policy tweaks.

The Pacific Rim’s shifting politics may tilt Washington’s calculus as well. Since the Nixon administration, Washington has prioritized a realpolitik relationship with Beijing over any attachment to Taiwan. America’s current stance toward China’s claims on Taiwan is implicit acquiescence. But Beijing’s growing assertiveness along its periphery has raised alarms for American allies in Tokyo, Seoul and Manila, all of whom are watching to see how China tests America’s defense commitments to Taiwan.

Ms. Tsai will not miss chances to remind Washington of the importance of that alliance. Her party intends to use its parliamentary majority to navigate Taiwan into the Trans-Pacific Partnership, an agreement that will hedge the island’s economy away from China and bind it more closely to America and its regional allies.

As Mr. Chen finished his stemwinder, the finale of Beethoven’s Fifth Symphony blasted over the speakers. “Protect our way of life, uphold our character ... come out to vote!” he implored. “Let’s give the Democratic Progressive Party a powerful start to its time in office!”