Utilize the input text as a context reference, choose the right relationship between 'Syriza' and 'Alexis Tsipras' from the options.
Options: parent organization, employer, chairperson, creator

Greek Prime Minister Alexis Tsipras tried to rally his Syriza party before a vote in parliament today (22 July) on the second package of measures demanded by international creditors to open talks on a new bailout deal.
chairperson