Despite the chaos in day-to-day politics and the fighting over issues like masks and lockdowns, Operation Warp Speed — the government’s agreement to subsidize vaccine companies’ clinical trials and manufacturing costs — appears to have been working with remarkable efficiency. It has put more than $11 billion into seven vaccine candidates, and the F.D.A. has said it will approve any one that is at least 50 percent effective at preventing infection or reducing its severity.

Moncef Slaoui, Operation Warp Speed’s chief scientific adviser and a former pharmaceutical executive who has overseen the development of 14 vaccines, has said repeatedly that he expects some of the candidates that he picked to have 75 to 90 percent efficacy and at least two to win approval by early January.