Nixon certified Kennedy’s election in 1960. Interestingly, Nixon also changed electoral votes for Hawaii from being his to being Kennedy’s, as votes came in long after Election Day when the electors were chosen

This was due to it being Hawaii’s first presidential election (it only became a state in 1959) and so the state government there had no experience running elections

This was the precedent Trump was hoping Pence would use to not certify Biden’s win