BRUSSELS (Reuters) - Following are some of the many possible contenders to succeed Jean-Claude Juncker as EU chief executive after elections to the European Parliament in May.

European Union's chief Brexit negotiator Michel Barnier attends an EU's General Affairs Council in Brussels, Belgium, September 18, 2018. REUTERS/Yves Herman

Apart from electoral uncertainty, it is unclear that national leaders will follow Parliament’s call for them to pick a European Commission president from among the lead candidates -- or Spitzenkandidaten -- of parties contesting the ballot.

CONSERVATIVES

MANFRED WEBER - An MEP for 14 years, the 46-year-old German has led the biggest EU parliamentary group since 2014. He has declared he will run and he can be confident of support from German Chancellor Angela Merkel despite his youthful years and lack of the government experience that is usual for Commission presidents.

Diplomats in Brussels say, however, Merkel could still drop Weber to secure another prominent job for Germany like the head of the European Central Bank, which also comes vacant next autumn.

MICHEL BARNIER - The EU’s chief Brexit negotiator ruled himself out of the race on Friday.

ALEXANDER STUBB - The former Finnish prime minister announced he will challenge Weber at an EPP nominating convention in Helsinki on Nov. 8. Stubb, 50, competes in “Iron Man” triathlons and is multilingual unlike Weber, who does not speak French, or Barnier, who rarely seems comfortable in English.

Many other names cited have included Merkel allies PETER ALTMAIER and URSULA VON DER LEYEN and French IMF managing director CHRISTINE LAGARDE -- not to mention the wild card of ANGELA MERKEL herself, who is now in her fourth term.

SOCIALISTS

MAROS SEFCOVIC - The Moscow-educated Slovak diplomat who has worked in Brussels since 2004 and is Juncker’s vice president for energy said in June he would run. He is 52.

Sources in Brussels say he stands no chance in the top job race but will be Bratislava’s pick for a portfolio in the next Commission.

Slideshow ( 2 images )

CHRISTIAN KERN - Austria’s former chancellor, Kern is known for his strongly pro-European stance. He said earlier this month he would seek to win a seat in the European Parliament next May.

FEDERICA MOGHERINI - The 45-year-old was catapulted into the high-ranked Commission post of EU foreign policy chief in 2014. She could benefit from efforts to promote female candidates and a better left-right balance in Brussels but may struggle to get the necessary support from the new populist coalition in Rome.

HELLE THORNING-SCHMIDT - Danish prime minister until 2015, at 51 she is perennially cited as a center-left hope for senior EU roles but lacks backing from the ruling right in Copenhagen.

FRANS TIMMERMANS - Juncker’s Dutch deputy, 57, is a former foreign minister and passionate, multilingual advocate for the EU but his party’s national eclipse counts against him.

PIERRE MOSCOVICI - Former French finance minister, 60, now EU economics commissioner, his party’s national disarray is also a disadvantage, as is German wariness over his commitment to Berlin’s vision of a euro zone of tight public finances.

NADIA CALVINO - Long a senior Commission civil servant, at 50 she has the rare distinction for EU Socialists of being in government, having been named Madrid’s economy minister in June.

LIBERALS

GUY VERHOFSTADT - Former Belgian prime minister who leads the liberals in the EU parliament, his age (65) and outspoken advocacy of much more powers for Brussels may limit his appeal.

MARGRETHE VESTAGER - As a woman, aged 50 and with a star profile in Brussels from attacking tax avoidance and monopoly powers among U.S. multinationals like Google and Apple as the EU competition commissioner, the Danish former economy minister is widely talked about as a liberal who could win support beyond her party -- even if Denmark’s ruling conservatives oppose her.

CECILIA MALMSTROM - Another straight-talking, 50-year-old Scandinavian woman who has had a big role in Brussels’ tussles with Washington, the EU trade commissioner and former Swedish Europe minister could tick similar boxes to Vestager.

MARK RUTTE - Dutch prime minister for eight years, the 51-year-old may be tempted by a new job. He is solidly pro-EU but appeals to those who want its budgets and powers kept in check.

XAVIER BETTEL - In five years as Luxembourg prime minister, during which he married his male partner, the 45-year-old has built good relations with fellow national leaders. They might baulk at choosing another Luxemburger after Juncker, but his friendship with the even younger Macron could be an asset.

(This version of the story corrects the first name of the Danish politician in paragraph 20)