Portside

Turkey’s president, Recep Tayyip Erdoğan, and his Justice and Development party (AKP) face their greatest political challenge yet in elections on Sunday, with polls suggesting a united opposition could end his two decades in power.

Amid an economic crisis, and months after earthquakes killed more than 50,000 people and displaced millions more, the parliamentary and presidential votes will decide who leads the country of nearly 85 million and where it heads next.

Erdoğan has championed religious and conservative social values at home, presiding over an increasingly authoritarian regime that is more and more intolerant of criticism. Abroad, he has asserted Turkey’s influence in the region and loosened its ties with the west.

His main challenger is Kemal Kılıçdaroğlu of the secularist Republican People’s party (CHP), the unity candidate of the six-party Nation Alliance, who has pledged to reverse many of Erdoğan’s policies, including his all-powerful executive presidency.

How do the elections work?

In the presidential election, held every five years, any candidate who wins more than 50% of votes in the first round is elected president. If no one secures a majority, the election goes to a runoff – due on 28 May – between the two leading candidates.

In the parliamentary elections, held concurrently, the number of seats a party wins in Turkey’s 600-member parliament is directly proportional to the number of votes it receives, providing it gets – alone or as part of an alliance – at least 7% of the national vote.

Polling stations will open to Turkey’s 61 million voters at 8am local time on Sunday 14 May and close at 5pm, with results expected in the evening. An estimated 3 million voters resident abroad will have cast their ballots in advance.

Who are the presidential candidates and what do they stand for?

The country’s most powerful leader since Atatürk, who founded modern Turkey a century ago, Erdoğan, 69, has steered Turkey away from secularism and in 2018 abolished its parliamentary system, centralising power in the presidency.

From his 1,000-room palace outside Ankara, he in effect dictates government policy and has, critics say, eroded democracy, stifling dissent and bringing media and judges under his sway. His supporters say he has saved the country from serious security threats such as a 2016 coup attempt.

Economists also blame Erdoğan for the country’s economic crisis, saying his insistence on low interest rates has sent inflation soaring – to 85% last year – and caused the Turkish lira to lose 80% of its value against the dollar in five years.

Kemal Kılıçdaroğlu, a 74-year-old retired civil servant, has been Turkey’s main opposition leader for more than a decade, leading his CHP party to major victories in a string of big-city municipalities including Istanbul, Ankara and İzmir.

The candidate of the Nation Alliance or Table of Six has been criticised as lacking charisma and for blocking politicians from his own party – such as the high-profile mayors of Istanbul and Ankara – who may have stood a better chance of victory.

The alliance has prioritised justice, corruption and education, pledging to restore central bank independence, cut inflation, dismantle the executive presidency, restore parliament’s powers, return Syrian refugees, and improve relations with the west.

Perhaps critically, Kılıçdaroğlu has the support of the main pro-Kurdish Peoples’ Democratic party (HDP), which finished third in 2018 elections and faces a possible court-ordered closure over alleged links between some members and outlawed armed Kurdish militants. About 15% of Turkey’s voters are Kurdish.

Muharrem İnce of the rightwing, nationalist Homeland party has ignored criticism that by running he is splitting the anti-Erdoğan vote, and the rightwing Sinan Oğan, a former Nationalist Movement party (MHP) member, is running as an independent.

What’s on voters’ minds?

The election campaign has been dominated by the state of Turkey’s economy and the cost of living crisis, as well as the massive damage caused by the earthquakes and the question of which president and party alliance is best placed to improve matters.

The opposition has also attacked alleged government mismanagement of the rescue operation and fallout from the quakes, and accused it of failing to enforce building codes. The hard-hit, traditionally pro-Erdoğan east could prove crucial.

Why does it matter beyond Turkey?

Under Erdoğan, Turkey has flexed is military muscle in the Middle East and beyond, launching incursions into Syria, waging an offensive against Kurdish militants inside Iraq and sending military support to Libya and Azerbaijan.

It has also clashed diplomatically with Saudi Arabia, Egypt, the United Arab Emirates and Israel, rowed with Greece and Cyprus over maritime boundaries in the eastern Mediterranean, and been subjected to US arms industry sanctions after buying Russian air defences.

Erdoğan’s closeness to Russia’s president, Vladimir Putin, has led critics to question Turkey’s commitment to its fellow Nato members – which Ankara’s recent reluctance to endorse Sweden and Finland’s membership applications has only reinforced.

Turkey also, however, brokered a deal for Ukrainian wheat exports, underlining its potential role in ending the war. For the EU, defeat for Erdoğan would be strategically welcome but politically tricky, since it might relaunch Turkey’s accession bid.

What about the parliamentary elections?

Voters have a choice between 32 parties mostly organised into multiple alliances, at present headed by the People’s Alliance made up of the ruling AKP, the MHP, the Great Unity party (BBP) and New Welfare party (YRP).

The six parties making up the opposition Nation Alliance are the Republican People’s party (CHP), Good party (İYİ), Felicity party (SP), Future party (GP), Democrat party (DP) and Democracy and Progress party (DEVA).

The Green Left party (YSP, including Kurdish HDP candidates) and Workers’ party of Turkey (TİP) form the Labour and Freedom Alliance, while three leftwing parties are in the Union of Socialist Forces and two rightwing parties in Ancestral Alliance.

Who’s going to win, and what happens next?

In the presidential election, the most recent polling has shown Kılıçdaroğlu marginally ahead of Erdoğan by about two points but unlikely to obtain an absolute majority of votes, meaning a runoff is expected in a fortnight’s time.

Some commentators have warned that if Erdoğan loses by a small margin he may refuse to stand down, as happened when the AKP lost control of Ankara and Istanbul in municipal elections that it contested, even forcing a re-run in the latter.

In the parliamentary poll, the president’s AKP is on course to emerge as the largest single party, but the opposition Nation Alliance is projected to be the largest political bloc. Many analysts warn, however, that polling in Turkey is not always exact.

Jon Henley is the Guardian's Europe correspondent, based in Paris