Special election. Article I, Section 2: "When vacancies happen in the Representation from any state, the executive authority thereof shall issue writs of election to fill such vacancies."
It's a solid Red district but we'll see what happens with a special.
+17 points R according to the Cook Partisan Index (CPI). It wasn’t a competitive race in 2016. The Democrats will fly into a frenzy, but with the low turnout of special elections, that’s a very high mountain to climb. I doubt that they even have a competent party apparatus in that district.