Each political group represented at the European Parliament chooses a lead candidates (Spitzenkandidat in German) and it case of victory during the European Elections, this candidate will be proposed for the presidency of the European commission.
The procedure was introduced in 2014 with the aim of giving more democratic legitimacy to the nomination of the President of the European Commission by linking it directly to the results of the European Elections. The President Joncker (current President of the european commission) was the first Spitzkandidat chosen for office.
But being a Spitzenkandidat does not mean you’ll be automatically chosen as the President of the European Commission. The candidate has to be approved by the European Parliament and EU leaders.
Currently, we know the names of 2 Spitzenkandidaten:
Manfred Weber for EPP
Frans Timmermans for S&D
Jan Zahradil pour le ACRE
Ska Keller et Bas Eickhout pour le EGP