Take context from the input text and decide on the accurate relationship between 'Syriza' and 'Alexis Tsipras' from the options provided.
Options: chairperson, subsidiary, member of, distributed by

Greek Prime Minister Alexis Tsipras is trying to turn a corner after he reluctantly agreed to negotiate a third bailout, allowing the European Central Bank to top up bank credit lines but prompting a rebellion in his leftist Syriza party.
chairperson