Actually, he is a democrat now. He agreed to become a member to run in 2020.
" Along with his 2019 campaign announcement, he said he would abide by a new Democratic Party rule for presidential candidates and would affirm his membership in that party.[239] On March 5, 2019, he signed a formal statement, known as a "loyalty pledge," that he is a member of the Democratic Party and will serve as a Democrat if elected."
