BERLIN (Reuters) - Chancellor Angela Merkel will probably lose yet another powerful regional leader of her party on Sunday when Ole von Beust, the popular mayor of Hamburg, is expected to resign, German media reported on Saturday.
Von Beust, a charismatic 55-year-old who led the conservative Christian Democrats into power in the left-leaning port city in 2001 after 44 years of opposition, would be the sixth CDU state leader to leave office in the last 10 months.
The loss of von Beust, who local media say is fatigued in the job running Germany's second largest city, would be another severe setback for Merkel, whose popularity has slumped to the lowest level since she was elected in 2005.
Von Beust, a close ally of Merkel, engineered the first CDU-Greens coalition ever in 2008 -- establishing a precedent with Merkel's blessing for the right-left coalition and possible model for such a government at the federal level at some point.
Hamburg is one of Germany's 16 federal states. Von Beust was long viewed as one of the CDU's most influential leaders. Openly gay, von Beust has been a leading moderate voice in the CDU and helped make important inroads into new voter groups, especially in urban areas, that conservatives had long ignored.
A remarkably popular leader who even governed Hamburg with an absolute majority from 2004 to 2008, von Beust teamed up with the pro-environment Greens after the 2008 election.
The two parties, long considered at opposite ends of Germany's political spectrum, have worked together fairly smoothly in Hamburg. But a controversial school reform measure they agreed faces possible defeat in a referendum on Sunday.
The mass-circulation Bild and other media said that von Beuest planned to step down before the results of the referendum are announced. Bild said he planned to resign effective August 25 because he is tired of being in the spotlight.
"He wants to live a private life again -- no bodyguards and no more appointments," Bild said. Hamburg's interior minister, Christoph Ahlhaus, 40, will replace him, the newspaper said.
A spokesman for the Hamburg government declined to comment.
The departure in quick succession of experienced CDU state leaders will compound Merkel's difficulties, analysts say.
Thuringia's state premier Dieter Althaus quit in September after an election debacle, Baden-Wuerttenberg's state premier Guenther Oettinger left to become an EU commissioner in February and Christian Wulff of Lower Saxony quit in June after being elected federal president, a ceremonial office in Germany.
Hesse state premier Roland Koch has announced he will leave politics at the end of August. And Juergen Ruettgers, state premier of North Rhine-Westphalia, was beaten in an election in May and pushed out of office last week.
(Editing by Mark Heinrich)