Ltac start_unchanged :=
    red; intros; eapply one_leaderLog_per_term_unchanged; eauto; subst.(* solve invariant by lemma which shows leader logs do not change *)
  Ltac unchanged lem :=
    start_unchanged; apply lem.

Lemma wonElection_length : forall votes, wonElection votes = true -> length votes > div2 (length nodes).