it depends and varies for each election to the next with poll is closest. its trying to sample a (by comparison) small group of people and project that to figure what it would be overall. aside from the fact that its hard to get an accurate enough sample size, its also hard to predict this far out. many things can change between now and November. plus it always is thrown off when multiple people are on one side and one person is on the other. We'll see a little closer in the race