He hopped between rallies in North Carolina, Ohio and Wisconsin on Saturday as he sought to make up ground against his Democratic challenger Joe Biden.
Mr Biden, who holds a steady lead in national polls, campaigned in Pennsylvania, another key state.
Some 57 million votes have already been cast, a record spurred by the pandemic.
The Republican president has continued to hold packed rallies despite a new surge in coronavirus infections that is particularly affecting the Midwest - home to several electoral battlegrounds that could decide the election.
Speaking in Lumberton, North Carolina, Mr Trump said America's coronavirus epidemic had been blown out of proportion, and mocked his Democratic rival for making ominous warnings about a bleak winter.