Such data are published on the portal United States Elections Project, created by professor at Florida State University Michael McDonald.
According to his calculations, more than 46 million voters voted by mail, more than 23 million - in person.
The upcoming November 3 US general election will elect a president and vice president, 35 senators, all 435 members of the House of Representatives, 13 state and territory governors, and local government officials.
Earlier, American leader Donald Trump announced his leadership in the presidential race.