German Chancellor Angela Merkel's Christian Democrats (CDU) won a regional election in the German state of Hesse on Sunday, enabling it to form a coalition after 12 months of political stalemate, according to computer projections based on early returns, according to dpa. The centre-left Social Democrats (SPD), who govern at national level with the CDU, saw their share of the vote plunge to an historic low of 23.5 per cent after narrowly failing to unseat CDU Prime Minister Roland Koch in a closely contested election a year ago. The chancellor's conservative party was unable to profit from the SPD's poor showing, narrowly increasing its share of the vote to 37.4 per cent from the 36.8 per cent it polled in 2008. The CDU's preferred coalition partner, the liberal Free Democrats (FDP), was tipped to win around 16.1 per cent, giving the two parties a comfortable majority in the 110-member legislature in Wiesbaden. Hesse, one of Germany's most prosperous states where the financial centre of Frankfurt is located, has been administered for the past 10 months by a caretaker government led by Koch. Sunday's vote came less than a week after Merkel unveiled a 50-billion-euro (67 billion dollars) economic stimulus package designed to cushion the effects of a deepening recession. The vote kicked off a super election year, which sees five of the country's 16 states go to the polls, as well as elections for a new president in May, European elections in June and a general election on September 27. Voter support for the Hesse SPD had steadily eroded since a botched attempt to unseat Koch and form a minority government with help from the Greens and radical Left Party, which has its roots among former East German communists. Analysts said voters punished the SPD for a decision by its leader Andrea Ypsilanti to seek the backing of the Left Party, despite promising in campaign speeches that she would not do so. Ypsilanti announced her resignation as party chairman immediately after the first results were announced. The projections showed the Greens winning 14 per cent and the Left Party hovering slightly above the 5 per cent hurdle they need to clear for parliamentary representation. Around 4.4 million people were eligible to vote in the election.