McCain does not want to peak too early. Typically, the GOP does not win a presidential election until after the debates are completed, at which point paid advertising transcends months of sustained MSM bias. We are still in this race.
That does seem to have been the track record in the last races we’ve won. Once it’s the voters and the candidates, and the debates are half-forgotten, unless there have been major bites in them (which there hasn’t been in these), and we’re less filtered and muzzled by the media, we start pulling it out.