At the party congress over the weekend, 443 delegates voted for and 39 against the former education minister and current MP. Kajar Lember, Urve Palo, Indrek Saar and Helmen Kütt were elected as the four deputy heads.

Sven Mikser, Rainer Vakra, Andres Anvelt, Eiki Nestor, Ivari Padar, Karel Rüütli, Marianne Mikko, Mihkel Raud, Anto Liivat, Jaak Allik, Lauri Läänemets and Rannar Vassiljev were elected to the party's board.

Ossinovski wasted little time in making his mark, saying that the coalition agreement, between the Reform Party, IRL and the Social Democrats, only signed a few months ago, should be opened up for change. Although he later said the party's leadership mechanisms and internal democracy are top priority.

He said he will wait for the results of IRL's internal leadership elections and debate the agreement within his own party before deciding on a change proposals.

IRL will elected a new head on June 6, after current Chairman Urmas Reinsalu said he will not run after lower-than-hoped March 1 national election results. The Reform Party already held its internal election with Taavi Rõivas continuing as Chairman.

Jevgeni Ossinovski was born on March 15, 1986 in Kohtla-Järve, Estonia. He has an MSc degree on Comparative Politics from the London School of Economics and Political Science, an MA on Continental Philosophy from the University of Warwick and a BA in Philosophy from the University of Tartu.

He was elected to the Riigikogu (Estonian Parliament) in 2011 and was a member of the European Union Affairs Committee and the Foreign Affairs Committee. Ossinovski served as the Minister of Education and Research from March 2014 until April 2015.

Due to his background (he was born into Estonian Russian family), academic training and political experience, Ossinovski is well informed and familiar with integration issues between ethnic Estonians and ethnic Russians in Estonia.

When announcing his decision to stand for the party leadership in early May, Ossinovski said that in order to fulfill the aims of the Social Democrats, the party must participate in the coalition government, but they cannot compromise on most important principles. "It's not so much about whether we are in the government or not, but how to give the party back its confidence. We're not in politics to be popular or secure jobs for our members, but to find solutions to strategic questions the country is faced with, to make sure that Estonia and its society develop, and that it's a good place to live in – not just for one election cycle, but in twenty, fifty and one hundred years down the line."