On July 1, Spain will assume the rotating presidency of the Council of the EU until the end of the year. The last time there was a change of prime minister in the middle of a presidency was in 1996, in the always unstable Italy.
The decision of Pedro Sánchez will mean a logistical chaos of the first magnitude and a major administrative challenge. The focus is lost because the outgoing team would be aware of the campaign and its future and because the incoming one would have to take command.