With the European Parliament elections out of the way, leaders of the 28 nations that make up the European Union are preparing to select new heads for the EU's top five policy-making organizations.

The current terms of the presidents of the European Commission, the European Parliament and the European Central Bank, and the high representative of the union for foreign affairs and security policy are due to end Oct. 31, while the European Council chief's tenure will end Nov. 30.

The European Commission president is supposed to be chosen through the spitzenkandidat method, which sees the main European political parties nominate their respective lead candidates for the post ahead of the elections. The candidate with the greatest amount of parliamentary support is then appointed after approval from the national EU leaders.

However, the system is not enshrined in law and the reality is that the selection is made behind closed-door negotiations among heads of state, a process that has been criticized by ECB candidate Olli Rehn, among others, for being a political process that lacks meritocracy.

Under spitzenkandidat, Germany's Manfred Weber, leader of the European People's Party should be a strong contender for the job. However, his party lost ground during the election and he is opposed by Portugal and Hungary, while French President Emmanuel Macron has pointedly named a number of other worthy candidates without mentioning Weber's name. Weber's political career has been forged in the European Parliament, while the Commission is made up of heads of state and has been headed by a former head of state or government since Jacque Delors took the role in 1985.

The European Commission is the EU's politically independent executive arm which proposes legislation, enforces EU law and negotiates international agreements. The commission's president organizes the institution, sets a policy agenda and participates in meetings of the G-7 countries. The head is also responsible for providing political guidance to the commission, and may contribute to major debates in the European Parliament and between member governments at the European Council.

Luxembourg's Jean-Claude Juncker took the commission's helm in November 2014, and set out a 10-point plan for his term in office aimed to improve the EU's internal markets and international image. Toward the end of his term, 94% of the commission's proposals foreseen were submitted, with two-thirds getting adopted while the status of the remaining may depend on the institutional transition this year.

Manfred Weber, Frans Timmermans, Margrethe Vestager and Michel Barnier are among those tipped to succeed Juncker.

The European Council sets out the general political direction and priorities of the EU, but is not a legislative authority. The council consists of leaders of the EU member states, the European Council president and the European Commission president.

Donald Tusk succeeded Herman Rompuy to assume the role of the council's president in December 2014.

Tusk warned of dire consequences if Britain left the EU before the referendum and adopted a hardline approach in negotiations for a Brexit deal.

He aims to increase gender parity at the top level for the EU, saying there should be at least two women in leading roles though he remains unsure of its possibility.

Lithuania's president, Dalia Grybauskaitė, and Dutch Prime Minister Mark Rutte could contend to replace Tusk.

The European Central Bank manages the euro and the monetary policy of the bloc with euro as its currency. The central bank sets the inflation targets, manages the eurozone's foreign currency reserves, and ensures supervision of financial markets, and the soundness of the European banking system. Currently, the ECB is targeting inflation close to but below 2%.

Mario Draghi was appointed president of the ECB in November 2011, taking over the post amid slowing economic growth in the eurozone and fears of a recession. He famously pledged to do "whatever it takes" to save the single currency, which invited praise and criticism alike. Draghi expanded the central bank's range of monetary policy instruments and implemented the banking union.

Jens Weidmann, François Galhau, Benoît Cœuré, Erkki Liikanen and Olli Rehn are the potential candidates to succeed Draghi.

The president of the European Parliament oversees activities and committees of the legislative body, ensures that proper procedures are followed and gives the final approval for the EU budget. The president also represents Parliament within and outside the EU, and in its legal matters.

Italy's Antonio Tajani was appointed to the position in January 2017 for a 2.5-year term, and seeks reelection in 2019. Guy Verhofstadt and Mairead McGuinness may seek to replace Tajani.

The High Representative of the Union for Foreign Affairs and Security Policy is the principal coordinator and representative of the EU's foreign and security policy, and also responsible for representing the group at international forums such as the United Nations.

Italy's Federica Mogherini was appointed to the position in 2014 for a five-year term, and has led the "Europe in the World" project concerning matters including trade, humanitarian aid and crisis management, international cooperation and European neighborhood policy and enlargement negotiations.

So far, there are no names in the circulation for Mogherini's succession.