The waning support from parties in Angela Merkel’s center-right coalition, which voted Wulff into office 18 months ago, underscored how precarious his position is and the scandal risks becoming a major distraction for the chancellor as she grapples with the euro zone debt crisis.
Wulff’s resignation would reflect badly on Merkel because she pushed aggressively for his election over a popular opposition candidate in 2010.
Finding a successor could also prove a headache, unleashing a divisive political debate in Germany at a time when her government must show unity and resolve in combating the crisis.
The revelation on Monday that Wulff left an angry voice-mail message for the editor of top-selling Bild daily threatening legal action and even “war” if he published a story on a private home loan Wulff agreed at cheap rates has unleashed outrage.
On Tuesday, reporters from another paper, the Welt am Sonntag, said Wulff had tried to bully them too about a separate story.
Holger Zastrow, deputy chairman of the Free Democrats (FDP) who are junior partners in Merkel’s coalition, spoke out against Wulff, who was a top member of Merkel’s Christian Democrats (CDU) and state premier of Lower Saxony before becoming president, a largely ceremonial post.
“If a German president personally picks up the phone to ring an editor and leaves a mailbox message, this is not what I expect of a president,” he told broadcaster MDR, adding that Wulff had “a duty to explain himself.”
Other senior conservatives said they expected Wulff, whose next public appearance is scheduled for Friday, to give an account of himself in the coming days.
Thomas Oppermann, a senior figure in the opposition Social Democrats (SPD), said time had run out for Wulff. Only a week ago, SPD leader Sigmar Gabriel urged the president not to step aside, but the party appeared to be withdrawing its backing after the Bild revelations.
“The grace period is over,” said Oppermann. “No German president is above the law. That applies to press freedom, too. It is absolutely inappropriate if the president is trying to stop free reporting,” he said.
Wulff laid himself bare to attacks of hypocrisy by stressing the importance of press freedom in an apology he made last month about the home loan he received in 2008, when he was a state premier.
The loan raised questions about potential conflicts of interest and about whether he had misled the parliament in the northern state.
German media railed against the president.
“The mixture of naivety and brazenness with which Wulff has behaved is shocking... He is the head of state. This office is obviously too big for Wulff,” wrote the Sueddeutsche Zeitung.
Stefan Aust, a well-known author and former editor of Der Spiegel weekly, said Wulff appeared to be on a a “political suicide mission.”
“I have never experienced something as insane as this, to be frank,” Aust told WDR 2 broadcaster.
Opinion is growing among experts that Wulff, once seen as a potential rival to Merkel, will have to go.
“A German president simply can’t put pressure on the press like this. It’s not acceptable,” Peter Loesche, emeritus professor of political science at Goettingen University said, adding that prospect was unwelcome for Merkel.
“Merkel looks bad for not having vetted Wulff before she nominated him, for failing to check if there were any skeletons in the closet.”
Merkel would face the headache of finding a new candidate to be elected by the 1,244-member Federal Assembly, where her coalition has a slim 4-seat majority.
But there are no obvious successors. One possibility, Finance Minister Wolfgang Schaeuble, is widely seen as being indispensable in his current job during the euro zone crisis.
Other options could be conservative Labour Minister Ursula von der Leyen, who Merkel passed over in 2010, and the conservative president of the Bundestag lower house of parliament, Norbert Lammert.