By Thomas Escritt and Caroline Copley
BERLIN (Reuters) - Germany's Christian Democrats elected Armin Laschet as chairman on Saturday, aiming to unify their divided party behind a new leader who they hope can succeed Angela Merkel as chancellor when she steps down after federal elections in September.
Laschet, the premier of the western state of North Rhine-Westphalia - Germany's most populous - won a runoff vote against Friedrich Merz, securing 521 votes against 466 for his arch-conservative rival, according to a ballot of 1,001 party delegates.
At the helm of the CDU he replaces Europe's predominant politician and a consistent winner with German voters since taking office in 2005, who has said she will not run for chancellor again.
"I want to do everything so that we can stick together through this year... and then make sure that the next chancellor in the federal elections will be from the (CDU/CSU) union," Laschet said in his victory speech.
Laschet, 59, presents himself as the Merkel continuity candidate, and she said last year he had "the tools" to run for chancellor, the closest she has come to endorsing anyone.
By tradition, the CDU chairman is usually - though not always - the chancellor candidate for the CDU and its Bavarian sister party, the Christian Social Union (CSU), and the conservative bloc is on course to win September's federal ballot.
However, polls show Markus Soeder, the CSU leader, is the conservative most favoured by voters. Some CDU lawmakers want dynamic Health Minister Jens Spahn to run for chancellor, though he has backed Laschet for the party leadership.