How a Message of Unity and Mistakes by Erdogan Tipped the Istanbul Election

A focus group run by the opposition in April showed that ruling party voters were not against a recount, but strongly opposed a repeat election, said Gulfem Saydan Sanver, a political consultant who advised the opposition campaign.

“That was one of the main points that the A.K.P. missed,” she said.

“On March 31, educated conservatives came to us,” said Yuksel Taskin, a professor of political science and a prominent member of the opposition. “On June 23, we saw working class conservatives turn towards the C.H.P.”

One of the most important swings occurred among women, in particular those from lower and middle-income conservative families who had helped power the rise of Mr. Erdogan’s ruling party.

While his party had long campaigned against, and eventually removed, a ban on headscarves in public institutions and public universities, those same headscarf-wearing women turned against the party.

“Their goal was to be emancipated,” Mr. Bayar, the campaign strategist, said. “But, right now, these women with headscarves cannot find a place for themselves in a party that increasingly uses authoritarian language, because they are much more freedom oriented and they want to be in social life much more.”

He added: “Because they have experienced it themselves, they cannot tolerate injustice.”

In the end the ruling party underestimated its opponent, Mr. Imamoglu. The A.K.P. used to be very good at polling its constituents and gathering feedback from communities, said Ms. Sanver, but communication within the party has broken down and it has lost touch with its own supporters.

“I studied most of the A.K.P. campaigns since 2007,” she said. “I can easily tell you that this has been the worst political campaign they have ever done.”