Parties to the petition.

A petitioner shall join as respondent to his petition— (a) where he, in addition to claiming declaration that the election of all or any of the returned candidates is void, claims a further declaration that he himself or any other candidate has been duly elected, all the contesting candidates and where no such further declaration is claimed, all the returned candidates; and (b) any other candidate against whom allegation of any corrupt practice is made in the petition.