Parliament President Norbert Lammert says Koehler won 613 votes Saturday from a special parliamentary assembly to achieve a slim majority. The 1,224-member assembly comprises lower-house lawmakers and delegates nominated by Germany's 16 state legislatures.
The 66-year-old Koehler is a member of Merkel's conservative Christian Democrats and a former head of the International Monetary Fund.
Challenger Gesine Schwan of the center-left Social Democrats won 503 votes. The opposition Left Party's Peter Sodann was backed by 91 delegates and far-right candidate Frank Rennicke by four.
THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.
BERLIN (AP) - German President Horst Koehler hopes to secure a second five-year term on Saturday in an unusually tight parliamentary vote just months before the country chooses a new government.
Koehler, 66, is a member of Chancellor Angela Merkel's conservative Christian Democrats and a former head of the International Monetary Fund.
Polls show that he has become one of Germany's most popular politicians since taking the largely ceremonial presidency, but his re-election is not assured.
Gesine Schwan, 66, a center-left Social Democrat and former university professor, is challenging Koehler in a rerun of the 2004 presidential vote. She hopes to become the first female head of state.
A special 1,224-member assembly crammed into Berlin's glass-domed Reichstag parliament building to make the choice.
The presidency, which carries moral authority but little real power, is supposed to be above the political fray.
However, this year's contest comes four months before Merkel and Social Democrat Frank-Walter Steinmeier, her foreign minister, face off in a national election in which both hope to end their tense "grand coalition" of Germany's biggest parties.
Merkel, then Germany's opposition leader, installed Koehler in 2004 with the help of the pro-business Free Democrats, her preferred future coalition partner.
A defeat for Koehler would be a symbolic blow to Merkel before September's vote and a surprise success for the Social Democrats, who have been lagging in polls.
The choice was being made by a special assembly split equally between lower-house lawmakers and delegates nominated by Germany's 16 state legislatures. Those delegates included Germany's main Jewish leader, Charlotte Knobloch; national handball team trainer Heiner Brand; and retired boxer Regina Halmich.
Merkel's party and the Free Democrats have 604 votes. Together with the Free Voters, a small Bavarian center-right party, they could muster 614, just enough to re-elect Koehler.