Ltac use_entries_match :=
    match goal with
      | [ _ : eIndex ?e1 = eIndex ?e2,
              H : context [entries_match]
                              |- _ ] =>
        first [ solve [eapply H with (e:=e2)(e':=e1); eauto; congruence] |
                solve [eapply H with (e:=e1)(e':=e2); eauto; congruence]]
    end.

Lemma wonElection_one_in_common : forall l l', wonElection (dedup name_eq_dec l) = true -> wonElection (dedup name_eq_dec l') = true -> exists h, In h l /\ In h l'.