Of the 3,141 counties and county equivalents in the U.S., none has voted for the winner of every presidential election. Vigo County in Indiana has come close, backing 30 presidents starting in 1888, but its record was marred by its pluralities for William Jennings Bryan in 1908 and Adlai Stevenson in 1956.

But some counties matter more than others — especially those in states whose electoral votes are up for grabs. This year’s presidential nomination contests did not proceed according to form, with far more votes cast for Donald Trump and Bernie Sanders than almost any expert predicted. It’s not clear whether the patterns of partisan support that have mostly prevailed over the last two decades will be altered much in the general election; initial polling suggests, possibly misleadingly, that they will.