The June 3 Republican Senate primary in Mississippi was unprecedented, with incumbent Sen. Thad Cochran coming in a close second to challenger Chris McDaniel, forcing tonight's run-off. A swing of a few hundred votes in a few counties would have put either candidate over the 50 percent mark at that point.That may very well be true for tonight, as well.

We've created the following graph of Mississippi's 82 counties, listed by how strongly they favored either McDaniel (he dominated in Jones County, at the top) or Cochran (who won Hinds County) in the primary. (The vote margin in the primary is shown in light red.) As results come in, we'll update the graphic to show two things:

  • With a red bar, the margin of votes by which Cochran or McDaniel leads. If the red bar points left, Cochran leads. If it points right, McDaniel.
  • With a blue bar, the change in the percentage from the primary. If the blue bar points left, Cochran is doing better in the county than in the primary. If it points right, McDaniel is.

A tip: Keep an eye on those counties at the top and the bottom of the chart.

Last update: 11:10 pm Eastern. Precincts counted: 1,798 of 1,832. AP calls the race for Cochran.