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

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