Germany’s Greens have accused their opponents of dirty campaigning and hired a prominent libel lawyer to defend their lead candidate against plagiarism accusations, as the ecological party seeks to get its challenge for the chancellory back on track three months before the national elections. The Green party on Tuesday dismissed claims that its co-leader Annalena Baerbock had lifted five passages in her recently published book from news articles and Wikipedia entries without crediting them. “The accusations are without any basis,” said Christian Schertz, a lawyer whose list of past clients includes the footballer Cristiano Ronaldo, the Germany coach Joachim Löw and a string of German celebrities. Since the information cited was in the public domain, Schertz argued, the passages did not violate copyright law. “We are clearly dealing with another attempted campaign to Ms Baerbock’s disadvantage,” he said. A Green spokesperson described the plagiarism allegations as an attempt at “character assassination”. The accusations, which have been widely reported across German media, were originally voiced on a blog by the Austrian academic and “plagiarism hunter” Stefan Weber. Weber, whose website offers a paid-for plagiarism checking service plus “media and PR work”, has posted numerous articles about the Green politician on his blog since May. In a statement sent to the Guardian, Weber said he had fisked Baerbock’s book out of “scientific interest” and categorically denied having been commissioned to carry out his investigation. The passages cited by Weber in his blog – such as four sentences nigh identical to those in a 2019 article by the American political scientist Michael T Klare – are presented as context rather than original argument in Baerbock’s book. The relevant section from Klare’s article, in turn, summarises the position of the US defence department. While plagiarism accusations have proven a number one reason for political resignations in the Merkel era, they usually centre on politicians’ doctoral thesis. Baerbock’s book, entitled Now: How We Can Renew Our Country, is a mass-market nonfiction title in which the Green politician lays out her political philosophy, ghostwritten by a journalist. The plagiarism claims come on the back of a series of questions over Baerbock’s self-presentation that have frustrated her party’s attempt to fight a campaign on policy rather than personality issues. Even Green sympathisers concede that the debate had been kept alive partly due to unforced errors on Baerbock’s behalf. The broadsheet Die Zeit wrote that the question marks over the Green candidate’s CV and book had effectively punctured the image of Baerbock as detail-obsessed perfectionist in the Merkel mould. “That the election campaign would be tough, that sections of the public could not wait for the Greens to trip up – all that has been apparent for months,” wrote Die Zeit. “Ever more surprising that mistakes are being made precisely where they could have been easily avoided.” After a strong start, in which the Green party leapfrogged the conservative Christian Democratic Union (CDU) of Armin Laschet, Angela Merkel’s designated successor, the ongoing scrutiny of Baerbock’s credentials has also affected opinion polls. In a recent survey by Politbarometer, approval for the 40-year-old Green dropped below that of her two main rivals, Laschet and the Social Democrat Olaf Scholz. A Forsa poll published on Wednesday had the CDU at 30% of the national vote for the first time since March, with the polling institute’s director, Manfred Güllner, suggesting that swing voters were flocking to the conservative candidate out of “fear of a Green chancellor”.