We hear about turnout all of the time leading out to the election, as reporters fixate on the fact that the side that turns out the most voters win the election. But today I came across a story in BBC-Bulgaria that illustrates a case where turnout really does matter.

Incumbent Georgi Parvanov won a first round of Bulgarian presidential polls on Sunday, but low turnout forced a runoff against a nationalist who has fought against the country’s drive to join the European Union. A Gallup exit poll for private television station BTV showed Parvanov, the former head of Bulgaria’s ruling Socialist party, won 63.69 percent of ballots cast.

Under Bulgarian law, at least 50 percent of voters must cast ballots for a candidate to win in the first round, so Parvanov and Siderov must face off in an October 29 showdown.

Here is an example where you really do have to turnout voters to win; if you don’t have a high enough turnout, the margin of victory does not matter!