I don't think you can get to a prediction of electoral vote by adjusting the sampling of a nationwide poll. They can only sample popular vote, which they got correctly.
And right now, we are talking about approval polls. Approval polls are a measure (one of many, no doubt) of how good a job the president is doing, not a predictor of the next election (which is over a year away). I, for one, don't question his ability to win the electoral vote.