In 1923, the "People's Party", soon adding the word "Republican" to its name, declared itself to be a political organisation and announced the establishment of the Turkish Republic, with Atatürk as its first president.

As Turkey moved into its authoritarian one-party period, the CHP was the apparatus of implementing far reaching political, cultural, social, and economic reforms in the country.

The Grand National Assembly forces militarily defeated Greece, France, and Armenia, overthrew the Ottoman government, and abolished the monarchy.

The Progressive Republican Party faced allegations of involvement in the Sheikh Said rebellion and for conspiring with remaining members of the CUP to assassinate Atatürk in the İzmir Affair.

Atatürk's prime minister, İsmet İnönü, proposed the passage of the Law on Ensuring Peace which gave the government extraordinary powers.

[16] For the next two decades Turkey was under a paternalist one-party authoritarian dictatorship, with one interruption; another brief experiment of opposition politics through the formation of the Liberal Republican Party.

From 1924 to 1946, the CHP introduced sweeping social, cultural, educational, economic, and legal reforms that transformed Turkey into a republican nation state.

In the period of 1930–1939, Atatürk's CHP clarified its ideology from a vague left-wing-Unionism for 'The Six Arrows': republicanism, reformism, laïcité, populism, nationalism, and statism, as well as borrowing tenets from Communism and (Italian) Fascism.

With the Ottomanism question settled, Turkish nation-building was prioritized which saw nationalist propaganda, language purification, and pseudo-scientific racial theories propagated.

In the party's third convention, it clarified its approach towards the religious minorities of the Christians and the Jews, accepting them as real Turks as long as they adhere to the national ideal and use the Turkish language.

Atatürk mostly favored İnönü's policies, so economic development of the early republic was largely confined to state-owned enterprises and five-year plans.

On 12 November 1938, the day after Atatürk's death, his ally İsmet İnönü was elected the second president and assumed leadership of the Republican People's Party.

Under pressure by the new conservative parliamentary opposition and the United States, the party became especially anti-communist, and retracted some of its rural development programs and anti-clerical policies.

[25] Due to the winner-take-all system in place during the 1950s, the DP achieved landslide victories in elections that were reasonably close, meaning the CHP was in opposition for 10 years.

Ecevit adopted a distinct left wing role in politics and, although remaining staunchly nationalist, attempted to implement democratic socialism into the ideology of CHP.

The CHP achieved its best ever result in a free and fair multi-party election under Ecevit, when in 1977, the party received 41% of the vote, but not enough support for a stable government.

As such, in the election of 1999, the DSP benefited massively in the polls at the expense of CHP, and the party failed to exceed the 10% threshold (8.7% vote), not winning any seats.

Since Baykal proclaimed the party to be the bulwark of the secularist establishment, the CHP assisted undemocratic attempts by the army and judiciary to shut down the newly elected AKP.

The crisis began with massive protests by secularists supported by the CHP in reaction to the AKP's candidate for that year's presidential election: Abdullah Gül, due to his background in Islamist politics and his wife's wearing of the hijab.

The CHP's campaign focused on the alleged İrtica (Islamic reaction) that the AKP victory would bring into government, which served to alienate liberals and democrats from the party.

[32] Without quorum, Erdoğan called for a snap election to increase his mandate, in which the CHP formed an electoral alliance with the declining DSP, but gained only 21% of the vote.

Following the decision, the AKP government, in a covert alliance with the Gülen movement, began a purge of the Turkish military, judiciary, and police forces of secularists in the Ergenekon and Sledgehammer trials, which the CHP condemned.

By a thin margin, parliament vetoed invading Iraq, due to half of the AKP's parliamentary group voting with the CHP against war.

[37] CHP leadership briefly held a soft Euroscepticism as the AKP government came close to an assension plan with the European Union (see Ulusalism).

[40] This support went so far as to help the government pass a law to lift parliamentary immunities, resulting in the jailing of MPs from the HDP, including Selahattin Demirtaş, as well as CHP lawmakers.

Despite the government's lackluster response to the economic crisis, COVID-19 pandemic, and the Kahramanmaraş earthquake, Kılıçdaroğlu lost his bid to Erdoğan after taking the race to a run-off and receiving 48% of the vote.

[47] On 19 July 2023, a 14-minute part of the Zoom conference between İmamoğlu and other prominent CHP officials, discussing the future strategies of the party, was leaked on YouTube.

Under the reformist leadership, CHP achieved an unexpected victory by defeating Erdoğan's AK Party in the 2024 Turkish local elections, for the first time in two decades.

[74] Some leftists critical of Kemalism criticize the party's continuous opposition to the removal of Article 301 of the Turkish penal code, which caused people to be prosecuted for "insulting Turkishness" including Elif Şafak and Nobel Prize winner author Orhan Pamuk, its conviction of Turkish-Armenian journalist Hrant Dink, its attitude towards minorities in Turkey, as well as its Cyprus policy.

It has traditional ties to the middle and upper-middle classes such as white-collar workers, retired generals, and government bureaucrats as well as academics, college students, left-leaning intellectuals and labour unions such as DİSK.