After Taiwan’s president, Lai Ching-te, launched a broad drive this month against what he warned was expanding Chinese subversion and spying, the backlash was swift.

Across the Taiwan Strait, Beijing hit back, sending a surge of military planes and ships near the island and warning that he was “playing with fire.” In Taiwan, Mr. Lai’s opponents accused him of dangerously goading China.

But Mr. Lai is wagering that he can — and, his supporters say, must — take a harder line against Chinese influence now, notwithstanding the threats from Beijing and the possibility that Taiwan’s opposition parties will dig in deeper against his agenda.

Mr. Lai appears to have concluded that China will limit its actions against Taiwan while Beijing focuses on trying to negotiate with President Trump over the escalating trade war, said David Sacks, a fellow at the Council on Foreign Relations who monitors Taiwanese affairs.

“The best guess is that he assessed that, if he was going to do this, he should do it at a time when China doesn’t want something to complicate its discussions with the United States,” Mr. Sacks, in an interview, said of Mr. Lai’s security steps.