"If schools are able to do it, then they should," Steinbrück said in response to a question from the audience during a campaign appearance in Berlin. A Reuters reporter noted that the comment was greeted with silence. Steinbrück then added that the step should be taken "out of consideration for religious convictions."

Not surprisingly, critique from Merkel's Christian Democrats was immediate. Barbara John, formerly in charge of integration issues for the city-state of Berlin, told the newspaper Bild that the debate was antiquated and that "children and parents have to get used to the fact that genders here grow up together and live with the same rights."

She was seconded by Serkan Tören, a member of the federal parliament with the Free Democrats, Merkel's junior coalition partner. Tören, himself from Turkey, told the tabloid that "dividing boys and girls is akin to dividing society. Splitting classes by gender is also the wrong signal to send when it comes to integrating Muslims in Germany."

But even the Greens, ostensibly the SPD's allies in the campaign, have distanced themselves. Memet Kilic, a member of parliament and the Green's expert on integration issues, said on Friday that current rules governing physical education classes should not be changed, emphasizing that gender equality is a universal human right.