Utilize the input text as a context reference, choose the right relationship between 'Syriza' and 'Alexis Tsipras' from the options.
Options: distributed by, developer, chairperson, platform

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