Hours before President Trump was set to return to the campaign trail in Florida on Monday, the nation’s top infectious disease expert, Dr. Anthony S. Fauci, warned that holding large rallies was “asking for trouble” with cases of the coronavirus surging in many states.

Dr. Fauci, in an interview with CNN, said that Americans needed to be more cautious in the fall and winter months, and warned that rising rates of infections in a number of states suggested Americans should be “doubling down” on precautions rather than casting them aside.

“We know that that is asking for trouble when you do that,” Dr. Fauci said of Mr. Trump’s decision to begin a full schedule of campaign rallies. “We’ve seen that when you have situations of congregate settings where there are a lot of people without masks, the data speak for themselves. It happens. And now is even more so