Ypsilanti was a member of the Hessian Landtag (parliament) and served as chairperson of the Social Democratic Party (SPD) of Hesse from March 2003 to January 2009.

However, after a "grand coalition" with the CDU was ruled out, Ypsilanti ultimately decided to cooperate with the Left Party in order to be elected prime minister and overcome the deadlock.

However, one day prior to the election, three other SPD representatives - Carmen Everts, Silke Tesch, and Jürgen Walter (vice chairman of the Hesse SPD) - also announced that they would vote against her, making it impossible for Ypsilanti to gain the needed majority.

On 8 November 2008, Ypsilanti withdrew her candidacy in favor of Thorsten Schäfer-Gümbel, who became the SPD's new lead candidate (Spitzenkandidat).

Preliminary election results on 18 January 2009 indicated that the CDU and the (FDP) together won 64 seats in the parliament - five more than the 59 required - and thus could begin forming a governing coalition.