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.

Greek Prime Minister Alexis Tsipras on Wednesday faced down a major mutiny in his radical left Syriza party and violent protests in the streets of Athens to win parliamentary approval for the tough reforms by creditors.

Answer: chairperson