If any person who has lodged a petition has, in addition to calling in question the election of the returned candidate, claimed a declaration that he himself or any other candidate has been duly elected and [the High Court] is of opinion—
(a) that in fact the petitioner or such other candidate received a majority of the valid votes; or
(b) that but for the votes obtained by the returned candidate by corrupt *** practices the petitioner or such other candidate would have obtained a majority of the valid votes, [the High Court] shall after declaring the election of the returned candidate to be void declare the petitioner or such other candidate, as the case may be, to have been duly elected.