Analyze the relationship between 'Syriza' and 'Alexis Tsipras' within the context of the input sentence.
Options: chairperson, director/manager, owner of, employer

Left-wing Syriza party leader Alexis Tsipras speaks to his supporters at Syriza's partyâ€™s main electoral center in Athens, Sunday, Sept. 20, 2015.
chairperson