Yang, a former Democratic presidential candidate who outlasted governors and senators in the nominating race despite sporting a thin political resume, is again running in a crowded primary field packed with candidates with beefier governing or business experience. And he’s again dogged by concerns that he has too little know-how to be running for office in such a time of crisis. In this race, however, Yang is an early front-runner, a distinction that provides a broader profile but also forces him to address questions about his experience more forcefully than he ever had to in his long-shot presidential bid.