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, Sept 20 The leftist Syriza party of Alexis Tsipras has won 35.07 percent of the vote in Greece's national election, according to data on the Interior Ministry website based on 10.16 percent of votes counted.
chairperson