The Powell Court held that the constitutional grant of power extends “to judg[ing] only the qualifications expressly set forth in the Constitution” and that “the [Senate is] without authority to exclude any person, duly elected by his constituents, who meets all the requirements for membership expressly prescribed by the Constitution.” 395 U.S. at 521-522, 548.
The Powell Court was focused exclusively on the Article I qualifications, sidestepping any discussion of additional qualification imposed by Article VI, Clause 3: “The Senators … shall be bound by oath or affirmation, to support this Constitution[.]” The Court explained that it did not consider whether this provision, or the other provisions concerning dual office-holding or disqualification because of impeachment or rebellion, was a qualification because the parties agreed that “Powell was not ineligible under any of these provisions.” Id. at 520 n.41.
So, what if the individual does not have the capacity to take the oath? Could the Senate exclude that individual? Consider the case of John M. Niles, elected to the Senate in 1843….
What should Senator Collins do? It seems that she should offer a resolution delaying the administration of the oath to Moore pending an inquiry into his capacity to take the oath; such a resolution is privileged and prevents the Presiding Officer from administering the oath. Riddick’s Senate Procedure, S. Doc. 101-28 at 704 (1992). This is certainly the procedure used by Jarnagin in the Niles precedent. While “orderly procedure” first outlined in 1903 suggests that a Senator-elect should be sworn first and then his qualifications should be reviewed, that procedure seems to relate primarily to cases of election contests and not to cases where the Senator lacks capacity to take the oath. See id. at 704-705. Moore can then take his case to a Federal district court and thence on appeal, eventually to the Supreme Court. Poetic, I think.
Senator Collins, if you feel as you say, it’s worth a try. Good luck.