Well the point in time we're looking at is July. According to Gallup, Reagan held a lead of a few points throughout July and into August. And Ford was the incumbent whether elected or not.
But that's not really the issue. If you look at the trend lines on Gallup's site for presidential elections, polls prior to the conventions have little bearing on the outcome of the election. In fact, in Gallup's case anyway, it is remarkable how many times the last poll prior to the election was off by enough to make a difference in the outcome. Polls can show trends, but are very poor at predicting the actual vote.