It appears that prime minister Zapatero is sometimes referred to as president Zapatero in Spain, because he is "president" of the government. In America, prime ministers tend to be called prime ministers, but for the record, Scheuneman can claim some technical validity here.
This article available online at:
http://www.theatlantic.com/daily-dish/archive/2008/09/president-zapatero/211471/
