TAIPEI, Taiwan — On a drizzly Tuesday night earlier this month, Chen Li-hung, a celebrity news television host, strode onto a stage in Changhua, in central Taiwan, and launched into a passionate speech, feeding red meat to his Democratic Progressive Party’s assembled faithful.

“My parents are from mainland China,” he told the crowd. “Yet I was born in Taiwan. I grew up in Taiwan. So why did the teachers in school tell me I am still Chinese? Since my youth, I have felt that I am not Chinese, I am Taiwanese!” He ripped into the incumbent president, Ma Ying-jeou. “Eight years ago, President Ma won himself a pretty nice electoral victory, but he is walking us closer and closer to China, and has Taiwan gotten any better?”

For hours, speakers like Mr. Chen raised the crowd to a fever pitch. Then Tsai Ing-wen, the party’s presidential nominee, arrived to cool them down.

Ms. Tsai, a former law professor and trade negotiator, let her surrogates fire up the base during the election campaign that ended on Jan. 16 in victory for her and her party. She knew that if voters detected too much populism, they would have turned on her. And she realized that Beijing and Washington watch her words closely.