U.S. ConstitutionArticle I — The Legislative BranchSubarticle 2Section 4
When vacancies happen in the Representation from any State, the Executive Authority thereof shall issue Writs of Election to fill such Vacancies.
Use as reference
Lexinter.net | U.S. Const. art. I, § 2, cl. 4 | https://laws.lexinter.net/constitution/us/article-1/section-2/clause-4