After almost a full term as the party’s shadow finance minister, he pulled out of national politics and was then elected Mayor of Aarhus in 2006.

[2][3] When Helle Thorning-Schmidt led the Social Democrats to victory in Denmark's 2011 elections, Wammen returned to Danish Parliament (representing Aarhus), securing the fifth-highest number of personal votes.

[5] Under his leadership as Minister of Finance, the parliament approved a cash handout to the elderly and other measures totalling 3.1 billion Danish crowns ($439 million) to cushion the impact of soaring inflation and high energy prices in 2022.

[6] After a year and a half studying law, Wammen switched to political science,[2] and earned a master's degree from the University of Aarhus in 2001.

[7] In 2011 Danish newspaper Ekstra Bladet reported that Wammen fathered a son, Carl, (born 9 October 2011) with Julie Rademacher, a former member of the Parliament whom the paper described as "a friend".