When does the campaign for president end

An election for president of the United States happens every four years on the first Tuesday after the first Monday in November. The next presidential election will be November 3, 2020

Explanation:

the governor can not veto a referendum that the voters approve

copernicus finished the first manuscript of his book, "de revolutionibus orbium coelestium" ("on the revolutions of the heavenly spheres") in 1532. in it, copernicus established that the planets orbited the sun rather than the earth. he laid out his model of the solar system and the path of the planets.