Take context from the input text and decide on the accurate relationship between 'Syriza' and 'Alexis Tsipras' from the options provided.
Options: parent organization, chairperson, creator, employer

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