Former President Ion Iliescu has resigned from the party he created after Romania threw off communism 20 year ago.
The 80-year-old Iliescu says he is leaving the Social Democratic Party to concentrate on writing and reflecting.
Romanian politicians say they are shocked by Iliescu's decision, announced late Tuesday to cotidianul.ro, and some have urged him to reconsider.
Iliescu is considered one of the country's most temperate politicians, though he has been criticized for his communist past. He served three terms as president during most of the 1990s and from 2000 to 2004.
The Social Democrats vote for a new leader Saturday. It is in disarray after previous leader Mircea Geoana lost the December presidential election.