Nate Silver’s polling tracker now has Trump slightly favored to win (50.2%) the election. While this shift appears small, it has drawn attention because it pushes Trump just past the halfway mark in forecasts for winning the Electoral College.
Silver explains that while Trump’s rise over recent weeks is significant, and his polling model, is designed to minimize overreactions to new data to provide more accurate long-term predictions (i.e., it’s likely a “real” effect), this doesn’t in any way mean Trump “will” win, and the race remains highly competitive, especially in key states like Michigan, Wisconsin, and Pennsylvania, which are critical to determining the outcome.
The lines don’t show popular vote, but chance to win. And either Trump or Harris is going to win, so p(Harris) = 1 - p(Trump). The lines must mirror each other. Since polls always have uncertainties and current events influence voting behaviors, of course the exact percentages fluctuate.