Utilize the input text as a context reference, choose the right relationship between Syriza and Alexis Tsipras from the options. Options: product/material produced, manufacturer, distributed by, industry, position held, original broadcaster, owned by, founded by, distribution format, headquarters location, stock exchange, currency, parent organization, chief executive officer, director/manager, owner of, operator, member of, employer, chairperson, platform, subsidiary, legal form, publisher, developer, brand, business division, location of formation, creator.

ATHENS, July 23 Greek Prime Minister Alexis Tsipras faced down a revolt by rebels in his leftists Syriza party to win parliament's backing on Thursday for a second package of reforms required to start talks on a financial rescue deal.

Answer: chairperson