Get CandidateElections serialized into an object with
        party-slug keys.

def get_candidates_by_party(self):
        """
        Get CandidateElections serialized into an object with
        party-slug keys.
        """
        candidate_elections = CandidateElection.objects.filter(election=self)

        return {
            ce.candidate.party.slug: ce.candidate for ce in candidate_elections
        }