Utilize the input text as a context reference, choose the right relationship between 'Syriza' and 'Alexis Tsipras' from the options.
Options: director/manager, chief executive officer, creator, chairperson

Greek Prime Minister Alexis Tsipras faced down a revolt by rebels in his leftists Syriza party to win parliament's backing for a second package of reforms required to start talks on a financial rescue deal.
chairperson