What is the relationship between 'Syriza' and 'Alexis Tsipras' in the context of the input sentence.
Options: owner of, distributed by, manufacturer, chairperson

In Athens, Prime Minister Alexis Tsipras and his inner circle debated whether to take on anti-bailout rebels in his own radical left Syriza party by calling a parliamentary confidence vote or to go straight to early elections.
chairperson