Take context from the input text and decide on the accurate relationship between 'Syriza' and 'Alexis Tsipras' from the options provided.
Options: chief executive officer, chairperson, subsidiary, developer

Greek Prime Minister Alexis Tsipras was on Wednesday mulling whether to hold early elections after the austerity bailout split his radical left Syriza party, leaving him powerless to push further reform bills through parliament.
chairperson