If they sit in the seat, they assume the responsibilities of the oath.

 new court filing reveals that Kamala Harris, Merrick Garland, and other leading Democrats in the Biden Administration, including Defense Secretary Lloyd Austin, Homeland Security Secretary Alejandra Mayorkis, and Transportation Secretary Pete Buttigieg, have no oath of loyalty to the US Constitution on file, as required by law. https://nationalfile.com/court-filing-kamala-harris-merrick-garland-violate-us-code-have-no-oath-of-office-on-file/