Ole von Beust, the governing mayor of the Hamburg, will leave office as of August 25. With the widely expected move, Angela Merkel's government lost another powerful ally.

Two other key Hamburg politicians also announced they would leave politics. The popular 55-year-old mayor of Germany's second largest city, a state in its own right, is a state premier in all but title.

He is the latest in a long line of leading members of Chancellor Merkel's Christian Democratic Party (CDU) to throw in the towel. "Everything has its moment," Von Beust told reporters in Hamburg on Sunday, listing the positions he has held in Hamburg. "This, naturally, applies to me as well."

He has been suffering form fatigue in his mayoral duties and has lost his appetite for politics altogether, aides have told German media. Leaving office alongside von Beust are senator for culture, Karin von Welck and Volkmar Schoen of the Senate Chancellery.

Cross-party appeal

A charismatic speaker, often touted as Merkel's potential understudy, Beust helped the CDU reach new urban voter demographics that the traditionalist party had often ignored.

The openly gay, centrist conservative conquered the traditionally left-leaning port city of Hamburg for the Christian Democrats (CDU) in 2001, after the party had spent 44 years in opposition.

He has retained the post ever since, and even ruled with an absolute majority - a rare occurrence under Germany's electoral system - between 2004 and 2008.

Von Beust had been governing Hamburg in coalition with the Green party - the highest-profile alliance in the history of two parties considered at opposing ends of the political spectrum - and the city has been running relatively smoothly despite the right-left divide.

As Hamburg law calls for all of the city's senators, who serve in positions similar to ministers in other German states, to be reconfirmed in office if the head of government steps down.

It remains to be seen if the rest of Hamburg's government will remain in office or if early elections will be held.

One area of legislation where the parties have struggled is an adaptation to the city's schooling system.

Also on Sunday, Hamburg's electorate is voting on a referendum over the proposal.

Merkel's popularity has sunk to its lowest level since she was elected chancellor in 2005, and an exodus of senior CDU politicians has hardly helped steady the ship as she walks the tightrope of trying to cement Germany's economic recovery while simultaneously cutting national public spending.

Von Beust is the sixth Christian Democrat state premier to leave his post in the last 10 months. Although Christian Wulff quit his job in Lower Saxony to be promoted to the role of German president, he was replacing perhaps the highest profile CDU-affiliated deserter of all, former President Horst Koehler.

Still, the CDU remains the dominant party in German politics, despite its waning popularity.

Deutsche Welle/Germerica