That's a little strong. From this pair of articles, it looks like a President's approval ratings are a poor estimator of their reelection chances when considered 2 years away, but quite a good one when considered 6 months out. The volatility in opinions seems to operate on timescales of several months.

Nate will of course include factors other than current polling averages in his forecasts, but those averages are the main component, even with the uncertainty in a few months' time.