Brussels - European parliamentary groups are not fully-fledged parties, but loose federations of national movements, roughly organised by ideology.

By tying themselves to a political grouping or family at the European level, MEPs and their national parties potentially receive substantial EU funding, plum jobs and can collectively negotiate laws, even though lawmakers often take direction from national capitals and not their hierarchy in parliament.

Spending from EU coffers must be devoted to official European projects and functions, a rule that has often been overlooked with several cases of parties syphoning European cash to national campaigns.

Here's an overview:

- European People's Party (EPP) -

Member parties include CDU/CSU (Germany), Les Republicains (France), Forza Italia (Italy), Partido Popular (Spain), Fidesz (Hungary).

The EPP is led by CSU politician Manfred Weber. The 46-year-old engineer has been a member of the European Parliament since 2004 and parliamentary party leader of the European People's Party since 2014.

With 216 out of 751 MPs, the EPP is was by far the strongest faction in the European Parliament, but looks certain to lose some feathers in the next election.

- Party of European Socialists (PES) -

Member parties include: the SPD (Germany), SPO (Austria), Parti Socialiste (France), Partito Democratico (Italy), Partij van de Arbeid (Netherlands)

Dutchman Frans Timmermans leads the Social Democrats' campaign. He is the first Vice-President of the European Commission and deputy to the EPP's Jean-Claude Juncker.

The 57-year-old, who speaks six languages, was foreign minister of the Netherlands from 2012 to 2014.

- European Green Party (EGP) -

Member parties include: Bundnis 90/Die Grunen (Germany), Europe Ecologie (France), Die Grunen (Austria), Miljopartiet de grona (Sweden)

The European Green Party is once again competing with two lead candidates. As in 2014, 37-year-old German Ska Keller is in the top duo. This time she is partnered with the 42-year-old environmental scientist Bas Eickhout from the Netherlands.

- Alliance of Liberals and Democrats for Europe (ALDE) -

Member parties include: FDP (Germany), Open Vlaamse Liberalen en Democraten (Belgium), Democraten 66 (Netherlands)

The Liberals have not agreed on a single candidate for the EU Commission leadership, but a "top team" of seven personalities.

The most prominent member, alongside former Belgian prime minister and ALDE parliamentary group leader Guy Verhofstadt, is 51-year-old EU Competition Commissioner Margrethe Vestager from Denmark. FDP candidate Nicola Beer from Germany is in the "Team Europe".

The group is expected to be buoyed after the vote by supporters of French President Emmanuel Macron, running in the Renaissance list.

- European Free Alliance (EFA) -

Member parties include: Schleswigsche Partei (Denmark), Bayernpartei (Germany), Esquerra Republicana de Catalunya (Spain).

The EFA sees itself as an association of regional parties in Europe. Its top candidate is the Catalan independence leader Oriol Junqueras, a 50-year-old who is imprisoned in Spain.

He faces 25 years in prison in Catalonia for the 2017 independence referendum, which Madrid declared illegal.

- European Left Party -

Member parties: The Left (Germany), Communist Party (France), Syriza (Greece), United Left (Spain).

In 2014, the European Left Party entered the race with today's Greek Prime Minister Alexis Tsipras. In 2019, the party elected joint leaders Violeta Tomic (56) from Slovenia and Nico Cue (62) from Belgium.

- Alliance of Conservatives and Reformers in Europe (ACRE) -

Member parties include: Law and Justice (PiS, Poland), Conservative Party (United Kingdom), Liberal-Conservative Reformer (Germany), Fratelli d'Italia (Italy)

The top candidate of ACRE is the 56-year-old Czech Jan Zahradil, who is also chairman of the party.

Most of the members of the Parliamentary Group of the European Conservatives and Reformists (ECR) are represented in Akre.

Key facts on the European Parliament

- Europe of Nations and Freedom (ENL) -

Member parties include: FPO (Austria), Die blaue Partei (Germany), Lega (Italy), Rassemblement National (former Front National, France).

The right-wing populist group officially rejects the concept of the top candidate. But this did not prevent the leader of the xenophobic Italian Lega party, Matteo Salvini, from claiming the post of Commission President if the right-wing populists became the strongest force in the European elections.