“People nationwide, including the entire bureaucratic elite, feel once more lost in uncertainty about the direction of the country and about their own personal security, and the rising anxiety has spread into a degree of panic throughout society,” Professor Xu wrote in an essay that appeared on the website of Unirule Institute of Economics, an independent think tank in Beijing that was recently forced out of its office.

“It’s very bold,” Jiang Hao, a researcher at the institute, said in an interview. “Many intellectuals might be thinking the same, but they don’t dare speak out.”

Professor Xu urged Chinese lawmakers to reverse the vote in March that abolished a two-term limit on Mr. Xi’s tenure as president. That near-unanimous vote of the party-dominated legislature opened the way for Mr. Xi, in office since late 2012, to retain power for another decade or longer as president, Communist Party leader and chairman of the military.