We’ve been publishing election models for more than 10 years now, and FiveThirtyEight’s 2018 House model is probably the most work we’ve ever put into one of them. That’s mostly because it just uses a lot of data. …
The principles behind the House forecast should be familiar to FiveThirtyEight readers. It takes lots of polls, performs various types of adjustments to them, and then blends them with other kinds of empirically useful indicators (what we sometimes call “the fundamentals”) to forecast each race. Then it accounts for the uncertainty in the forecast and simulates the election thousands of times. CONT.
Nate Silver, FiveThirtyEight