The court for the trial of contested elections for presidential electors or for the office of senator or representative in Congress shall consist of the chief justice of the supreme court, who shall be presiding judge of the court, and four judges of the district court to be selected by the supreme court, two of whom, with the chief justice, shall constitute a quorum for the transaction of the business of the court. If the chief justice should for any cause be unable to attend at the trial, the judge longest on the supreme court bench shall preside in place of the chief justice; and any question arising as to the membership of the court shall be determined by the members of the court not interested in the question.