Musk, an avid Trump supporter who has reportedly fathered 12 children with three different women, welcomed Vivian in 2004 with his first wife, Justine Wilson.
Investors reacted positively to the likelihood of a Trump win, as Wall Street rallied with the former president appeared set to defeat Vice President Kamala Harris.
Some social media users argued that the 54-year-old mother-of-one had been replaced with a body double for the cameras, citing the large sunglasses she wore indoors as evidence.
The letter was written to make it appear as though it came from the voter, accusing Wimbish of " 'give[n] me hell', 'conspiring votes' and 'distracting voters from concentrating'."