Germany's popular defense minister resigned Tuesday amid a deepening scandal over plagiarism allegations that threatened to become a liability for Chancellor Angela Merkel's conservatives in upcoming regional elections.
Karl-Theodor zu Guttenberg announced his decision days after Bayreuth University revoked his doctoral title. It said he had violated academic standards in his thesis by failing to sufficiently credit some of his sources.
Guttenberg, who initially called the allegations "absurd," later admitted "grave mistakes" but denied having deliberately deceived anyone. Merkel stood by him for nearly two weeks after the allegations emerged, arguing that they had no bearing on his work as defense minister.
However, a steady drip of allegations kept the scandal going, and Guttenberg said it threatened to overshadow policy issues such as a major overhaul of the German military and troops' mission in Afghanistan.
"It is the most painful step of my life," Guttenberg said as he announced his resignation at his ministry. "I am drawing the consequences that I have and would have demanded of others."
"Like others, I have to stand by my weaknesses and mistakes," Guttenberg said. "I will gladly concede to my opponents that I was appointed not to be the self-defense minister, but the defense minister."
Guttenberg submitted his doctoral thesis in 2007, five years after becoming a conservative lawmaker. German media reported late Tuesday he would also give up his seat in parliament. Guttenberg's office was not immediately reachable for comment.
Merkel said she accepted "with a heavy heart" the resignation of the 39-year-old, long rated Germany's most popular politician.
Guttenberg "is a person with outstanding political talent, with an exceptional ability to reach people's hearts and enthuse them for politics," she said.
Still, his departure may actually do her a favor, with six of 16 Germany's states due to hold regional elections this year. Three of those votes come in late March; one, in the southwestern state of Baden-Wuerttemberg, offers a tough test for Merkel's center-right coalition.
Although Guttenberg still inspired a degree of public sympathy, "he would have damaged his party if he hadn't resigned" and the scandal had dragged on, said Manfred Guellner, the head of the Forsa polling agency.
Guttenberg is a member of the Christian Social Union, the Bavaria-only sister party to Merkel's Christian Democratic Union. The CSU itself doesn't face voters this year, but Guttenberg had been expected to campaign for Merkel's party.
Guttenberg became the rising star of Germany's center-right after being thrust into Merkel's Cabinet two years ago as economy minister. He built a reputation as a plain-speaking man of action in that job and then, after Germany's 2009 election, as defense minister.
In recent months, he pushed through a plan to end conscription _ part of an effort to slim down the German military and make it better adapted to an era in which it faces growing demands to deploy overseas.
The chancellor said her government would carry through the "indispensable" reforms.
Merkel said it was too early to name a successor but a decision will be made "shortly." She added that Guttenberg's CSU has the right to nominate the new minister if it chooses to.
Germans appeared to agree it was time for Guttenberg to go.
"I think it's a pity because he was a good minister," said Monika Schmid, from Wangen in his home state of Bavaria. "At the end of the day, however, it was right _ because you just can't do that, plagiarize a thesis."
The resignation was "the logical consequence" of his actions, Berlin accountant Christiane Rost said. "But basically, this step has come a bit too late."
The opposition berated Merkel for clinging to Guttenberg even amid a growing outcry from the academic world.
Merkel "has embarrassed herself, her credibility is damaged and she has damaged the reputation of politics," said Thomas Oppermann, a senior lawmaker with the center-left Social Democrats.
Oskar Niedermayer, a political science professor at Berlin's Free University, said Merkel did herself few favors by trying to separate Guttenberg's activities as a politician and academic, since the allegations went to the heart of the credibility on which he built his political career.
Still, he said he doesn't see "serious negative effects for her in the long term."
Merkel held out hope of an eventual comeback for Guttenberg, who said he is committed to clearing up questions that remain over his dissertation.
"I am convinced that we will, in whatever form, have the opportunity to work together in the future," she said. For now, though, it's unclear whether he will seek to return.
"I was always ready to fight, but I have reached the limits of my strength," Guttenberg said as he ended his resignation statement.
Juergen Baetz contributed to this report.