“I was a Bernie supporter in 2016,” Mr. Yang joked at a recent campaign stop. “But now I’m here, and I am younger, fresher, more modern, more Asian, more tech-savvy than Bernie.

“I am like the Bernie of 2020,” he said.

The elder, whiter Mr. Sanders pushed back last week by saying Mr. Yang’s chief policy plan, a government-guaranteed universal basic income, isn’t the panacea Mr. Yang and his followers believe.

Mr. Sanders counters the guaranteed government payout with his own expansive promises, including a federal jobs guarantee and, of course, his signature “Medicare for All” universal health care plan.

Self-professed 2016 Sanders backers flooded chatrooms and messaging boards to testify to their conversion to Yangism.