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.

The vote, expected in the early hours of Friday, will test the strength of a rebellion by anti-austerity Syriza lawmakers, which could raise pressure on Prime Minister Alexis Tsipras to call snap elections as early as September.

Answer: chairperson