German President Joachim Gauck announced on Monday his decision against running for a second five-year term due to advancing age, presenting Chancellor Angela Merkel with another political headache ahead of next year's election.
The 76-year-old former pastor and human rights advocate from the former communist East Germany has held the largely ceremonial post of president since March 2012.
"This decision was not easy for me," Gauck said in a statement at his residence, Berlin's Bellevue Palace. "I would not like to assume that I can guarantee the energy and vitality for another period of five years [as president]."
Gauck added that a change in high office was part of the normal process of democracy, but said "the years between 77 and 82 are different than those that I'm in right now."
Even before his formal announcement, German media had begun speculating about his possible successor. The daily Bild reported at the weekend that he planned to step down from the post.
The list of possible candidates include: parliamentary speaker Norbert Lammert; Finance Minister Wolfgang Schaeuble; Foreign Minister Frank-Walter Steinmeier; and the head of Germany's top court, Andreas Vosskuhle.
During his four years as head of state, Gauck has been seen as restoring a sense of dignity and moral authority to the presidency after his two predecessors left office before the end of their terms.
"Gauck has returned the high moral integrity to the Office of the President,” German Justice Minister Heiko Maas.
His comments were echoed by Horst Seehofer, a key figure in Merkel's coalition government, who said Gauck had "given people a sense of orientation and brought them together."
The president is elected in secret ballot by the so-called Federal Convention, which altogether comprises more than 1,000 members.
This includes members of the lower house of parliament, the Bundestag, as well as a raft of delegates chosen by the nation's 16 states. This often includes celebrities and national figures.
However, the vote for a new president is also seen as a test of the political authority of the chancellor of the day. That could mean another test for Merkel, who has recently faced a barrage of criticism from within her own conservative political bloc for her handling of the nation's refugee crisis.
Merkel's two previous nominations, Horst Koehler and Christian Wulff, both resigned before their terms were out and as a result were seen as a political embarrassment to the chancellor.
Koehler stepped down following comments he'd made about Germany's military role in Afghanistan, while Wulff resigned amid allegations of a corruption scandal.
Leading political figures had spoken out in favour of Gauck seeking a second term so as to avoid complicating the build-up to the national election set for September 2017. The presidential election is expected in February.
Merkel, who is due to meet Gauck later Monday for routine talks, now has the choice of either deciding on a candidate from the ranks of her Christian Democrats (CDU) and their Bavarian-based Christian Social Union (CSU) allies, or seeking out a replacement who has much broader political appeal.
Gauck was elected to the office without any party affiliation.
But with an election on the horizon it might be difficult for Merkel to secure the backing of the major parliamentary parties for a common candidate.
The hard-left opposition Die Linke has already called on the left-leaning Social Democrats and the environmental Greens to join together behind one candidate.