Davis is the owner of I Squared R Element Company, a silicon carbide heating elements company that he founded in 1964. He is also known for filing a successful lawsuit against the Federal Election Commission in 2006, claiming that the so-called "millionaire's amendment" to McCain-Feingold Act was unconstitutional. The U.S. Supreme Court, with Justice Alito writing for the 5–4 majority, sided with Davis, striking down the millionaire's amendment as violating the First Amendment to the United States Constitution for fundamentally restricting the right of a self-financing candidate to spend his or her own money in a preferred way.