Our model is slow to move.

This is by design. Our model starts with a weighted average of polls in each state, giving polls conducted more recently and polls with a larger sample size a greater weight in the average. At this point in the election cycle, it uses a longer time window to calculate these averages. This steadiness means it is more stable and less inclined to chase after the most recent poll. But it also means it is slower to react to developing trends, such as recent polling that may indicate a tightening race. This can be a feature or a bug, depending on your perspective. Preconvention polls are informative, but history suggests that it is a mistake to place too much emphasis on a week’s worth of polling.

Let’s say you want to forecast the average margin of national polls for the next month. Would you rather take the average of the polls from the previous two weeks or average every poll from the previous two months? More often than not, you’d be better off taking the average of the longer period. This informs the approach taken by our model.

That said, we expect the simulations in our model to converge rapidly over the next month or two, as the conventions end and polling becomes more predictive of the final outcome.

Distributions are more interesting than averages.

Our estimate for Mrs. Clinton’s lead over Mr. Trump nationally is 3.7 points; our friends at FiveThirtyEight have a slightly smaller estimate of 3.4 points, but our overall probabilities of winning differ by 12 percentage points. This is a small difference, but a notable one. We believe one source of the difference is in the ways we believe states will (or won’t) swing together, and how much they’ll shift.

This is illustrated best by seeing our electoral distributions side by side: The FiveThirtyEight histogram is wider and flatter than ours. It assigns a greater chance that something highly unusual will happen, while ours thinks that the course of this election will look pretty much like the ones that have come before it. For example, we think there is only about a 1 percent chance that Mrs. Clinton will get fewer than 160 electoral votes. The FiveThirtyEight model assigns that prospect an 8 percent chance.