Wulff, like von der Leyen a member of the conservative Christian Democratic Union, is now regarded as the top candidate to fill the shoes of President Horst Köhler, who resigned unexpectedly on Monday, according to several major media groups.
News magazine Der Spiegel reported that von der Leyen's candidacy faced strong opposition from CDU premiers, including Wulff, even though the 51-year-old mother of seven was Chancellor Angela Merkel's own preference.
Der Spiegel reported that Wulff had spoken to Merkel on Wednesday morning and stated his opposition to von der Leyen's appointment while also declaring his own readiness to take the post.
One source in the CDU camp told the magazine that it was now a “strong probability” that Wulff would be the conservatives' choice. Wulff, who is married with a young son and also has a daughter from a previous marriage, has been premier of Lower Saxony since 2003.
Quizzed on Thursday by reporters, Wulff said: “I'm happy as premier. Maybe I'll know more tonight.”
No official decision had been made, the Chancellery said. Merkel plans to consult with the CDU premiers on Thursday evening to present them with her choice for the post, reports said. Westerwelle is expected to speak with the corresponding deputy premiers at the same time.
Conservative political sources have said that one objection to von der Leyen's appointment is that it would be difficult to find a suitable replacement for the key portfolio of labour and social affairs.
Guido Westerwelle, the leader of the Free Democrats – the CDU's coalition partners – and Vice Chancellor, said there was no doubt the parties would come to a quick agreement on who to nominate.
“Conversations are being conducted constructively,” he said.
Even the CDU's Bavarian sister party, the Christian Social Union, with whom Wulff has not shared a particularly good relationship in the past, supported his candidacy, sources said.
There also appears to be opposition to von der Leyen in the FDP. Free Democrats politician Sebastian Blumenthal said young FDP members of the Bundestag opposed her candidacy partly because of her push as Family Minister to fight child pornography by blocking access to the internet – an approach criticised at the time as a misdirected censorship that wouldn't achieve its intended aim.
The government will need to settle the matter quickly to banish the troublesome distraction at a time when it has more than enough other problems, not least of which is finding savings in the nation's overstretched federal budget.
The Federal Convention, a special body consisting of the lower house or Bundestag and an equal number of representatives from the states, will vote on a new president on June 30, though the government is expected to announce its pick well before that – possibly this week.
The vote will then be a virtual formality, with the CDU and FDP coalition holding a clear majority in the Federal Convention.