In the context of the input sentence, determine the relationship between 'Syriza' and 'Alexis Tsipras'.
Options: headquarters location, currency, legal form, chairperson

While the result is a victory for Prime Minister Alexis Tsipras in that he managed to convince parliament to back him on the bailout, he did suffer a major rebellion from Syriza MPs for the second time in a week -- prompting analysts to predict he may be forced to call early elections.
chairperson