The big loser in the parliamentary elections held last weekend in Turkey was President Recep Tayyip Erdogan. Not only did his Justice and Development Party (AKP) lose its majority in the legislature, but the results were a rejection of the president's ambitions to claim additional powers. It is a stunning defeat for a master politician and heralds a period of instability in Turkish politics. The eventual outcome of this political struggle is unclear.

When he was first elected prime minister in 2003, Erdogan governed as a moderate Islamist reformer who challenged the secular elites who had ruled Turkey since its founding as a republic in 1923. Given the threat he posed to entrenched interests, in particular the military, he was forced to produce results. Economic liberalization jump-started the economy, making Turkey one of Europe's top performers. He reduced a long-standing source of domestic instability by extending rights to the Kurdish minority. And, most important, he was a moderate Muslim politician, who offered a middle course between Islamic extremists and secular conservatives. Indeed, many politicians saw Erdogan as a new type of Islamic leader who could bridge the gap between Muslims and the West as well as serve as a model for leadership in the Islamic world.

Unfortunately, that moderate image has dissolved in recent years as Erdogan has pursued campaigns to crush any opposition to him using every power at his disposal. He is quick to see conspiracies behind all opposition to him. He has arrested members of the military and police forces, politicians and journalists. He believes that an exiled Islamic leader has scattered a cadre of his own believers throughout the bureaucracy to undermine his government.

After serving the maximum permitted terms as prime minister, Erdogan was elected president in 2011. While that position has less power than his former post, it was widely understood that he was the real decision maker, not Prime Minister Ahmet Davutoglu. Yet even as Erdogan's formal powers diminished, he went about constructing what can best be described as a cult of personality. He dominated the media, offering commentary on issues ranging from Jewish conspiracies to women's "inferiority" to men. He started construction on the world's largest airport, which will bear his name, and in an especially outsized gesture, had a new presidential palace built — a 1,000 room structure that cost $600 million.

Meanwhile, in 2013 Erdogan had the police break up national protests that were prompted by his plans to raze a small park in central Istanbul. When the dust cleared 11 people had died and thousands were injured or arrested. Months later a corruption scandal erupted that claimed several Cabinet members; when it looked like Erdogan's son might be next, the prosecutor was fired, along with dozens of other police and justice officials in what the president called a strike against a conspiracy against him.

These developments, coupled with a slowing economy, undermined the president's support. When he called on voters — despite his constitutional duty as president to remain above politics and parties — to give his AKP a majority in the June 7 elections so that he could rewrite the constitution to claim even more power, they revolted.

That rejection takes on additional significance with the rise of the People's Democratic Party (HDP), a Kurdish nationalist party that managed to cross the 10 percent vote threshold, entering Parliament for the first time. The HDP presence, which will total 80 seats in the 550-seat Parliament, effectively denied AKP its majority. Erdogan and other party leaders will now be forced into negotiations to form a government. His first choice is likely to be the rightwing Nationalist Movement Party (MHP), but two big issues stand in the way. The first is Erdogan's readiness to bargain with the Kurds leaders. The second is the party's reluctance to accept the dominant role that Erdogan has been demanding.

A second option is a coalition with the Republican People's Party (CHP), a secular group that is the second largest group in Parliament. That would create a significant majority, but it too faces too big obstacles: the CHP's problems with the president's thirst for more power and Erdogan's belief that the party represents entrenched interests that the AKP was created to overthrow. The last time Turkey was forced to rely on coalition governments was in the 1990s and that decade was marked by rapid turnover of governments and military intervention in politics. That unhappy history of coalition governments could well resume.

Erdogan has a strong hand, however. If a government cannot be cobbled together after 45 days, then new elections must be called. His party won 41 percent of the vote and a significant number of voters later said that they would have voted differently if they had anticipated these results. It is a gamble, but Erdogan could between now and then remind the Turkish people of the stakes and all he has delivered. He has dominated Turkish politics for more than a decade and may yet turn the tide again. But that requires him to learn from this debacle and to restrain his ambition.