In the context of the input sentence, determine the relationship between 'Syriza' and 'Alexis Tsipras'.
Options: director/manager, location of formation, business division, chairperson

Greece's government on Tuesday submitted tough bailout terms demanded by eurozone creditors to parliament, as Prime Minister Alexis Tsipras battled for support for the draconian reforms from his ruling anti-austerity Syriza party.
chairperson