ANKARA, Turkey — Turkish President Recep Tayyip Erdogan, who is seeking a third consecutive term in office in elections in May, marks 20 years in power on Tuesday.

The 69-year-old, who served as prime minister from 2003-2014 and as president thereafter, started as a reformist who expanded rights and freedoms, allowing his majority-Muslim country to start European Union membership negotiations.

He later reversed course, cracking down on dissent, stifling the media and passing measures that eroded democracy.

The presidential and parliamentary elections set for May 14 could be Erdogan’s most challenging yet. They will be held amid economic turmoil and high inflation, just three months after a devastating earthquake that killed tens of thousands.

Here’s a look at some of the key dates during Erdogan’s rule:

March 27, 1994: Erdogan is elected mayor of Istanbul, running on the pro-Islamic Welfare Party ticket.

Dec. 12, 1997: Erdogan is convicted of “inciting hatred” for reading a poem that the courts deem to be in violation of Turkey’s secular principles, and sentenced to four months in prison.

Aug. 14, 2001: Erdogan, who broke away from the Welfare Party with other members of its reformist wing, forms the conservative Justice and Development Party, or AKP.

Nov. 3, 2002: A year after it is founded, AKP wins a parliamentary majority in general elections. Erdogan however, is barred from running due to his conviction.

March 9, 2003: Erdogan is elected to parliament in a by-election after his political ban is lifted.

March 14: 2003: Erdogan replaces his AKP colleague Abdullah Gul as prime minister.

Oct. 3, 2005: Turkey begins accession talks with the European Union after Erdogan’s government introduces a series of reforms.

July 22, 2007: Erdogan wins 46.6% of the votes in general elections.

March 31, 2008: Constitutional Court accepts an indictment seeking the AKP’s closure for acts allegedly in violation of secularism. The court eventually rules not to shutter the party but cuts treasury financing for political parties.

October 20, 2008: The first of a series of trials against military officers, lawmakers and public figures begins. The suspects are accused of plotting to overthrow the government, in what turn out to be sham trials based on faked evidence and designed to eliminate Erdogan’s opponents. The trials were later blamed on the network of U.S.-based cleric Fethullah Gulen.

Sept. 12, 2010: Erdogan wins a referendum on constitutional changes that allow the government to appoint high court judges, curb the powers of the military and ensure presidents are elected by a national vote rather than by parliament.

June 12, 2011: Erdogan wins general elections with a landslide 49.8% of the vote.

May 28, 2013: Nationwide anti-government protests erupt over plans to cut down trees in Istanbul’s central Gezi Park. Turkey’s largest ever protests result in eight deaths, while the government is accused of using excessive force against protesters.

Aug. 10, 2014: Erdogan wins Turkey’s first presidential election held by direct popular vote. Although the post is largely ceremonial, he is accused of exceeding his powers and meddling in the running of the country.

June 7, 2015: The AKP, headed by Ahmet Davutoglu after Erdogan became president, loses its majority in parliamentary elections, and is forced to seek a coalition.

Nov. 1, 2015: AKP regains a parliamentary majority in re-run elections following months of insecurity, including suicide bombings by the Islamic State group and reignition of a decades-long conflict with Kurdish militants.

July 15, 2016: Erdogan’s government survives a military coup attempt blamed on followers of U.S.-based cleric Gulen, a former ally. The failed coup results in nearly 290 deaths. The government then embarks on a large-scale crackdown on Gulen’s network, arresting tens of thousands and purging more than 130,000 from government jobs. Many media and nongovernmental organizations are closed down and the crackdown then expands to critics, including Kurdish lawmakers and journalists. The EU accession talks, which had made slow progress, are frozen amid the democratic backtracking.

April 16, 2017: Voters in a referendum narrowly approve switching the country’s political system from a parliamentary democracy to an executive presidential system, abolishing the post of prime minister and concentrating a vast amount of power in the hands of the president. Critics call the system a “one-man rule.”

June 24, 2018: Erdogan wins presidential elections with 52.59% of the vote, becoming Turkey’s first president with executive powers, while his party’s alliance with a nationalist party secures a majority in parliament.

June 22, 2019: Erdogan’s party loses re-run election for Istanbul mayor by a landslide after it contests March elections which the main opposition party’s candidate had narrowly won. It’s the first time since Erdogan’s mayoral win in 1994 that his party and its predecessors lose Turkey’s most important city.

Feb. 6, 2023: A powerful earthquake devastates parts of Turkey and Syria, killing more than 48,000 people in Turkey. Erdogan’s government is criticized for its poor response to the disaster and for failing to prepare the country for a large-scale quake.