Alternate Electors were selected in 2020 by Arizona, Georgia, Michigan, New Mexico, Nevada, Pennsylvania, and Wisconsin. They cast their Electoral College votes for President Trump in December 2020.[1]
The existence of these alternate slates enables the Senate alone -- or merely the Joint Session's presiding officer, who will be Vice President Mike Pence on January 6 -- to block certification of the Biden Electors.
It is not the first time that states have submitted competing electoral votes: during the controversial 1876 Presidential Election, four states (Louisiana, Florida, South Carolina, and Oregon) did the same.