(CNN) There's an old saying in Turkish politics: "Who wins Istanbul, wins Turkey." The country's biggest city and commercial heart is undoubtedly its biggest political prize and President Recep Tayyip Erdogan isn't about to give it up without a fight.

When Erdogan's governing Justice and Development Party (AKP) lost the Istanbul mayoral elections by a razor-thin margin against the opposition Republican People's Party (CHP) in March, the defeat was crushing.

His party also lost capital Ankara during the elections, but Istanbul was different. This was the President's hometown, where his party had ruled since the 1990s, and where he launched his political career as mayor in 1994.

Erdogan wasn't going to give up this financial powerhouse -- which has a bigger budget then some European countries -- easily.

True, he wasn't even a candidate in the March 31 mayoral election. But Erdogan still served as the face of his party's local campaign in what was widely seen as a referendum on his government.

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