Mr. Yang has pitched himself as a cleareyed businessman and former leader of a nonprofit organization who has diagnosed the root of America’s problems — automation — and proposed a solution: having the government give every adult citizen a “universal basic income” of $1,000 a month.

After spending much of 2018 and the early part of 2019 toiling on the campaign trail in relative obscurity, Mr. Yang has gained steam since the spring. He routinely places in the top seven in national polling averages of the Democratic race, though his numbers are still stuck in the low single digits.

As he has grown his following, which he calls the “Yang Gang,” donations have increased as well, allowing his once fledgling campaign operation to expand significantly and add more traditional infrastructure. In the fall, for example, the campaign spent more than $1 million on an ad buy in Iowa, the kind of investment that would have been strictly aspirational in the first year of Mr. Yang’s campaign.

Unlike another businessman, Michael R. Bloomberg, Mr. Yang does not have a personal fortune big enough to self-finance his campaign. Mr. Bloomberg, the billionaire former mayor of New York City, has already spent more than $100 million of his own money on television ads across the country and has crept above Mr. Yang in many national polls.

Mr. Yang was one of just seven candidates invited to the Democratic debate in Los Angeles last month, but his streak of qualifying for the events could end if he does not earn 5 percent support in multiple polls over the next two weeks.

Mr. Yang’s aides have long maintained that much of his support comes from disaffected voters who are underrepresented in the polls. The Iowa caucuses on Feb. 3 will provide the first test of that theory.

Patrick Healy contributed reporting.