Left to right is the calendar, Sept. 1 to Election Day. The runners are where the race stood that day.
The gap between them is our forecast's expected margin. One brick is one point.
Each gold block is one week of outside spending for that side, sized by the amount. "Boost" or "fizzle" says which way the race moved that same week. Spending isn't proof it moved the polls, and money shows up in the week groups reported spending it.
The "polls are off" slider moves every day's margin by the same amount. The what-if win chances are our estimate, using how sure the forecast was that day.