BERLIN, Aug 29 (Reuters) - Social Democrat Olaf Scholz won a televised debate on Sunday between the three leading candidates to succeed Angela Merkel as chancellor after Germany"s federal election on Sept. 26, a survey by pollster Forsa showed. The snap poll showed 36% of voters polled believed Scholz won, ahead of 30% for Greens candidate Annalena Baerbock and 25% for conservative Armin Laschet. Merkel, a conservative in power since 2005, plans to step down after the election.