The popular vote was an accurate predictor of delegate counts.

Who's winning, who's losing, and why.
June 6 2008 7:27 AM

Slate's Delegate Calculator

The popular vote proved an accurate predictor of delegate counts.

Illustration by Mark Alan Stamaty. Click image to expand.

With the dust settling on the Democratic nomination, it's worth a retrospective look at how successfully our calculator was able to estimate delegate counts based on a state's popular vote. While most states allocate the majority of their pledged delegates based on district-by-district vote totals, the proportion of delegates won by each candidate has historically been very similar to the statewide popular vote. This was the fundamental assumption of our calculator.

Of the 16 contests the calculator adjudicated after launching in early March, predictions based on the popular vote were off by an average of only 1.9 percent. Six states and territories reported final delegate tallies that exactly matched the calculator's prediction: Vermont, Wyoming, Guam, Indiana, Oregon, and Montana. The calculator was least successful in predicting Texas, which might be expected due to the state's Byzantine primary system.

Slate would like to thank the dozens of readers who wrote in challenging our numbers and suggesting new features for the calculator over the course of this project.

  • The current number of pledged delegates comes from NBC News' tally. The delegate count prior to March 4 includes the 14 pledged delegates from the Democrats Abroad Global Primary  and subsequent convention, who count for half as much as their domestic counterparts'.
  • We estimate the number of delegates based on the overall state vote, even though delegates are awarded by congressional district as well. We felt comfortable making this approximation because in the primaries through Mississippi, there was only a 2.9 percent deviation between the percentage of the overall vote and the percentage of delegates awarded in primaries. The proportion of delegates awarded by congressional district, therefore, does not differ greatly from the statewide breakdown.
  • The calculator does not incorporate superdelegates into its calculations. Superdelegates are unpledged and uncommitted and therefore can change their endorsements and convention votes at any time. As a result, we've simply noted at the bottom of the calculator how many superdelegates the leading candidate needs to win the nomination in a given scenario.
  • All of the calculator's formulas and data come from Jason Furman, the director of the Hamilton Project at the Brookings Institution.

Chris Wilson is a Slate contributor.



Slate Plus Early Read: The Self-Made Man

The story of America’s most pliable, pernicious, irrepressible myth.

Rehtaeh Parsons Was the Most Famous Victim in Canada. Now, Journalists Can’t Even Say Her Name.

Mitt Romney May Be Weighing a 2016 Run. That Would Be a Big Mistake.

Amazing Photos From Hong Kong’s Umbrella Revolution

Transparent Is the Fall’s Only Great New Show

The XX Factor

Rehtaeh Parsons Was the Most Famous Victim in Canada

Now, journalists can't even say her name.


Lena Dunham, the Book

More shtick than honesty in Not That Kind of Girl.

What a Juicy New Book About Diane Sawyer and Katie Couric Fails to Tell Us About the TV News Business

Does Your Child Have Sluggish Cognitive Tempo? Or Is That Just a Disorder Made Up to Scare You?

  News & Politics
Sept. 29 2014 11:45 PM The Self-Made Man The story of America’s most pliable, pernicious, irrepressible myth.
Sept. 29 2014 7:01 PM We May Never Know If Larry Ellison Flew a Fighter Jet Under the Golden Gate Bridge
Dear Prudence
Sept. 30 2014 6:00 AM Drive-By Bounty Prudie advises a woman whose boyfriend demands she flash truckers on the highway.
  Double X
Sept. 29 2014 11:43 PM Lena Dunham, the Book More shtick than honesty in Not That Kind of Girl.
  Slate Plus
Slate Fare
Sept. 29 2014 8:45 AM Slate Isn’t Too Liberal, but … What readers said about the magazine’s bias and balance.
Brow Beat
Sept. 29 2014 9:06 PM Paul Thomas Anderson’s Inherent Vice Looks Like a Comic Masterpiece
Future Tense
Sept. 30 2014 7:36 AM Almost Humane What sci-fi can teach us about our treatment of prisoners of war.
  Health & Science
Bad Astronomy
Sept. 30 2014 7:30 AM What Lurks Beneath The Methane Lakes of Titan?
Sports Nut
Sept. 28 2014 8:30 PM NFL Players Die Young. Or Maybe They Live Long Lives. Why it’s so hard to pin down the effects of football on players’ lives.