Refer to the input text as context and select the correct relationship between 'Syriza' and 'Alexis Tsipras' from the available options.
Options: platform, chairperson, developer, distributed by

Greek Prime Minister Alexis Tsipras on Friday reshuffled his government, a day after a major lawmaker mutiny in his radical left Syriza party over a draconian bailout deal.
chairperson