Given the input sentence, please extract the subject and object containing a certain relation in the sentence according to the following relation types, in the format of "relation1: word1, word2; relation2: word3, word4". Relations include: 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 conservative New Democracy party has only an interim leader after former prime minister Antonis Samaras quit as party chief in July after Greeks overwhelmingly supported Tsipras's call to reject an EU bailout at a referendum.

Answer: chairperson: New Democracy, Antonis Samaras