On election night, knowing who is ahead isn’t enough.

In states like Virginia, Georgia and elsewhere, cities have traditionally been among the last to report their votes. Because cities lean Democratic, this pattern means that returns for Democratic candidates will appear weaker than they actually are for a few hours after the polls close. Similarly, in states with slow-counting Republican areas, Republican candidates will seem weaker than they actually are.

The worst election analysts use these changes to tell comeback stories, asserting that a candidate was trailing early in the night but made up ground.

More sophisticated analysts interpret leads through the lens of the outstanding votes. “There’s a lot of votes left to be counted in heavily Democratic Cuyahoga County,” Jeff Greenfield said on CNN in 2004. “Remember, some of the votes outstanding are down here in Marion County where Obama is winning,” John King said on the same network in 2008.

This year, The Upshot will aim to let you be your own John King. In about a dozen of the closest Senate races, we, like many others, will track the leads reported by The Associated Press. But we will also adjust those leads based on what we know about where the votes have come from. Our adjusted leads will be based solely on current and historical returns. They will not use data from exit polls, or any forecasts from Senate models. You’ll be able to find a link to the tracker on The Times’s midterm page and The Upshot’s home page.