Karl-Theodor zu Guttenberg, 39, was stripped of his doctorate last week after apologising for errors he made with attributions. "There will always be people who find pleasure in publicly blaming him for mistakes in his doctorate," said the Saxony-Anhalt state premier, Wolfgang Boehmer. "I don't know how long he will be able to endure it." Mr Guttenberg, who has been consistently rated Germany's most popular politician in polls and named as a possible future chancellor, has rejected opposition demands to resign.