In 2008, half the presidential primaries were over on February 12. By contrast, in 2012, half the presidential primaries won’t be over until April 13. Because there is a slight difference between Democratic presidential primary dates (or the existence of Democratic presidential primaries) and Republican presidential primaries, this calculation uses the Republican presidential primaries.

The only state that had a presidential primary in 2008, but which won’t have one in 2012, is Washington. There were 41 presidential primaries in 2008 and 40 in 2012 (counting D.C., but not any territories). Not all presidential primaries are binding. The only states in 2012 that won’t hold presidential primaries are Alaska, Colorado, Hawaii, Iowa, Kansas, Maine, Minnesota, Nevada, North Dakota, Washington, and Wyoming. All presidential primaries are paid for by taxpayers, except that the South Carolina Republican presidential primary is paid for partly by the party and partly by the taxpayers.

UPDATE: when this blog post was first published, it said the median date was April 3. Afterwards, Ohio shifted from March to June, and that altered the median date, so this post was updated on October 26.