The Economist calls it “one of the most audacious challenges ever to the rule of Recep Tayyip Erdoğan, the Turkish prime minister.” In a police operation, a mayor, a construction tycoon, and the sons of three of Erdoğan’s cabinet ministers were arrested as part of a corruption probe. The juicy details were leaked to the press: “$4.5 million in cash packed in shoe boxes found in the home of the chief executive of a state-run bank; a money-counting machine and piles of bank notes discovered in the bedroom of a government minister’s son.”In retaliation, the government dismissed Istanbul’s police chief and at least 30 other top police officials, saying the corruption probe was a nefarious plot to undermine Erdoğan. Now Turkey’s stock exchange is slipping, and so is the lira.The turmoil comes in the wake of a fallout between Erdogan and Fethullah Gülen, a mysterious but extremely popular cleric who lives, strangely enough, in Saylorsburg, Pennsylvania. But don’t mistake his distance for a lack of influence. Gulen runs a number of media outlets and a network of hundreds of charities and schools in Turkey and beyond.Even in our world of weird political figures, Gülen stands out. Most people have never heard of him. He’s secretive, quiet, yet influential. And rich. He is, according to his website, an “authoritative mainstream Turkish Muslim scholar, thinker, author, poet, opinion leader and educational activist who supports interfaith and intercultural dialogue, science, democracy and spirituality and opposes violence and turning religion into a political ideology.” No one seems to know how many educational, advocacy, and media institutions his organization runs, nor who or where his followers might be (City Journal speculates: “There are somewhere between 3 million and 6 million Gülen followers—or, to use the term they prefer, people who are “inspired” by him.”), nor what his political goals are, if any.Gülen and Erdoğan, both Islamists, are ideologically similar. And they were partners when Erdoğan first came to power in 2002. It is only recently that their fallout became apparent, after Erdoğan attempted to phase out many of Turkey’s charter schools, many of them owned by the Gülen movement.The police corruption probe, and the ensuing dismissal of police officials, appears to be an ugly tit for tat, as both groups attempt to publicly shame the other for graft and other crimes. This comes at a particularly significant time for Erdoğan as his party, the AKP, prepares for municipal elections in April next year. The election will be seen as a referendum on Erdoğan himself. While he still commands tremendous support, it is unclear exactly what might happen as the rift between him and Gulen grows wider. Success for the AKP in April just became a lot less assured.