Politicians and media outlets have questioned whether Ms. Tsai’s doctoral dissertation is authentic, even though her alma mater, the London School of Economics, has confirmed that it is.
Dennis Peng hosts a daily YouTube show dedicated to proving otherwise. His channel has 173,000 subscribers. Theories about Ms. Tsai’s dissertation have circulated in China, too, with the help of the Chinese news media.
Mr. Peng, a former television anchor, once supported Ms. Tsai. He was proud that Taiwan elected a female president. Now he says he is not being paid by anyone, including China, to crusade against her.
He is not worried about being smeared as fake news.
“Let news and fake news compete against each other,” Mr. Peng said. “I trust that most people aren’t so stupid. Everybody eventually figures it out.”
Steven Lee Myers contributed reporting. Wang Yiwei contributed research from Beijing.