Dissatisfaction with Kasselakis led the party to a prolonged internal crisis, resulting in a motion of no confidence and new elections scheduled for November 2024.

Although Syriza was launched in 2004, before that year's legislative election, the roots of the process that led to its formation can be traced back to the Space for Dialogue for the Unity and Common Action of the Left (Greek: Χώρος Διαλόγου για την Ενότητα και Κοινή Δράση της Αριστεράς, Chóros Dialógou gia tin Enótita kai Koiní Drási tis Aristerás) in 2001.

[23] It was made up of various organizations of the Greek political left, that, despite different ideological and historical backgrounds, held common ground in several important issues that had arisen in Greece in the late 1990s, such as the Kosovo War, privatizations of state businesses, and social and civil rights.

[citation needed] After the 2004 legislative election, the smaller parties accused Synaspismos of not honoring an agreement to have one of its members of parliament resign so that Yannis Banias of the AKOA could take his seat.

[citation needed] Three months after the 2004 legislative election, Synaspismos chose to run independently from the rest of the coalition for the 2004 European Parliament election in Greece and some of the smaller parties of the coalition supported the feminist Women for Another Europe (Greek: Γυναίκες για μια Άλλη Ευρώπη, Gynaíkes gia mia Álli Evrópi) list.

[33] This change of attitude was further intensified with the election of Alekos Alavanos, a staunch supporter of the coalition,[34] as president of Synaspismos, after its former leader, Nikos Konstantopoulos, stepped down.

The coalition ticket in the municipality of Athens was headed by Alexis Tsipras, proposed by Alavanos who declared Synaspismos' "opening to the new generation".

[citation needed] Opinion polls had indicated that Syriza was expected to make significant gains in the election, with predictions ranging from 4% to 5% of the electorate.

Tsipras achieved considerable popularity with the Greek electorate, which led to a surge in support for Syriza in opinion polls, up to 18 percent of the vote at its peak.

[42] At the end of June 2008, Start – Socialist Internationalist Organisation (Greek: Ξεκίνημα – Σοσιαλιστική Διεθνιστική Οργάνωση, Xekínima – Sosialistiké Diethnistikí Orgánosi) announced that it would join the coalition.

[44] In the 2009 Greek legislative election held on 4 October, Syriza won 4.6% of the vote (slightly below its 2007 showing), returning thirteen MPs to the Hellenic Parliament.

[citation needed] In June 2010, Ananeotiki (Reformist Wing) of radical social democrats in Synapsismós split away from the party, at the same time leaving Syriza.

[citation needed] In a move of voters away from the parties which participated in the coalition government under the premiership of Lucas Papademos in November 2011, Syriza gained popular support in the opinion polls, as did the KKE and DIMAR.

Delegates supporting the Left Platform (Greek: Αριστερή Πλάτφορμα, Aristerí Plátforma) led by Panayiotis Lafazanis, which wanted to leave the door open to quitting the euro, secured 30% (60) of the seats on Syriza's central committee.

[50] A modest success was also claimed by the Communist Platform (Greek section of the International Marxist Tendency), who managed to get two members elected to the party's central committee.

Syriza's main success was the election of Rena Dourou to the Attica Regional governorship with 50.8% of the second-round vote over the incumbent Yiannis Sgouros.

Its biggest disappointment was the failure of Gabriel Sakellaridis to win the Athens Mayoralty election, being beaten in the second ballot by Giorgos Kaminis with 51.4% to his 48.6%.

[citation needed] On 13 September 2014, Syriza unveiled the Thessaloniki Programme, a set of policy proposals containing its central demands for economic and political restructuring.

[57] Tsipras was congratulated by French president François Hollande who stressed Greco-French friendship, as well as by leftist leaders all over Europe, including Pablo Iglesias Turrión of Spain's Podemos and Katja Kipping of Germany's Die Linke.

"[58] The Financial Times and Radio Free Europe reported on Syriza's ties with Russia and extensive correspondence with the Russian political scientist Aleksandr Dugin.

[59][60] Early in the SYRIZA-led government of Greece, the Russian President Vladimir Putin and Tsipras concluded a face-to-face meeting by announcing an agreement on boosting investment ties between the two nations.

[65] Following the acceptance of the third memorandum with the institutions on Greece's debt by Tsipras and the Syriza government, 25 Syriza MPs who rejected the terms of the bailout, including the party's Left Platform and the Internationalist Workers Left faction, split to form a new party Popular Unity (Greek: Λαϊκή Ενότητα, Laïkí Enótita, LE).

His business background, his lightning-fast rise, and the publication of his earlier writings supporting Kyriakos Mitsotakis and New Democracy have brought him into conflict with prominent party members and former ministers.

Due to the fall in support for New Democracy, Syriza managed to close the difference in vote share between the two largest parties from over 20% in the legislative elections to 13.3%.

[91][92][93] On 7 September 2024, 100 members of the party's central committee tabled a censure motion against Stefanos Kasselakis after he had rejected their initial request for new elections.

As of 9 November, the leadership candidates are MP Pavlos Polakis, Sokratis Famellos, MEP Nikolas Farantouris and former mayor/actor Apostolos Gletsos.

The main constituent element of the original coalition was Synaspismos, a democratic socialist party, but Syriza was founded with a goal of uniting left-wing and radical left groups.

[112] Tsipras clarified that Syriza "does not support any sort of Euroscepticism",[113] though the party was seen by some observers as a soft Eurosceptic force for advocating another Europe free of austerity and neoliberalism.

[6] Tsipras stated that his goal was to build a broad progressive front without abandoning the party's core ideology and left-wing coalition.

Another member of the group was Tassos Koronakis, the former secretary of the Syriza Central Committee who resigned following the announcement of the snap elections in September 2015.