The limits and detriments of Turkish President Recep Tayyip Erdogan's one-man rule are becoming increasingly clear. Under Turkey's new executive presidential system, Erdogan has faced a barrage of crises. Turkey's shaky alliance with Russia has shown signs of strain, and its relations with the United States have continued to falter. U.S. President Donald Trump's administration, in fact, stands ready to impose more sanctions on Turkey if Erdogan's government fails to release American detainees by mid-October. For the beleaguered Turkish economy, the additional sanctions could be crippling. Given the costs of his foreign and economic policies, Erdogan's recalcitrant stance and obstreperous persona on the international stage seem to run counter to Turkey's interests. But not to Erdogan's. The Turkish president is acting out of little more than a desire to appear strong and to defy perceived opponents, including allies. His objective is to preserve his image at home as a leader who...