For Turkey’s Erdogan, a challenge in former stronghold

By DEREK GATOPOULOS and ZEYNEP BILGINSOY
ISTANBUL — Turkish President Recep Tayyip Erdogan hasn’t lost many elections since the conservative party he co-founded took control of the government in 2002. But the party’s rare defeat in Istanbul, Turkey’s largest city, was a political and personal setback for the country’s leader.
Opposition candidate Ekrem Imamoglu’s win Sunday in a repeat vote for mayor broke the lock the president’s Islamist-rooted party l