Chairman of the EPP Group in the European Parliament Manfred Weber | Patrick Seeger/EPA EU rules would bar Commission hopeful Weber from holding two posts German front-runner for center-right nomination has declined to rule out becoming leader of his CSU party.

Manfred Weber, the favorite to be the center-right nominee for European Commission president, has suggested he could do the top Brussels job while also leading his Christian Social Union party back home in Bavaria — but EU rules say otherwise.

“I have shown to this day that I am able to combine my tasks in Europe and for the CSU well,” Weber told weekly Bild am Sonntag at the weekend, when asked if he could do the CSU leader's job, currently held by Horst Seehofer.

But a revised code of conduct for European commissioners, approved earlier this year, explicitly rules out holding party positions with "management responsibilities." That would seem to preclude Weber from being both Commission president and leader of the party. The CSU leader is powerful figure in German politics who wields considerable influence, particularly in the context of the CSU's governing alliance with its sister party, the Christian Democratic Union currently led by Chancellor Angela Merkel.

The rules permit commissioners to participate in national politics "as members of national political parties or an organization of the social partners (such as trade unions) or in a national election campaign, including regional or local elections, provided that this does not compromise their availability for service in the Commission and the priority given to their Commission duties over party commitment." And it allows "the holding of honorary or non-executive functions in bodies of the party structure." But it specifically "excludes management responsibilities."

The code also states that commissioners "shall abstain from making public statements or interventions on behalf of any political party or organization of the social partners of which they are members, except when standing for election/participating in an election campaign" — another stipulation that would seem to rule out Weber holding both posts.

Weber, the leader of the European People's Party (EPP) group in the European Parliament, is the heavy favorite to be chosen as the EPP Spitzenkandidat, or lead candidate for Commission president, at a party congress in Helsinki this week. Former Finnish Prime Minister Alexander Stubb is challenging him for the nomination.

At the moment, of course, Weber is guaranteed neither job — and nothing would seem to bar him from seeking the two posts simultaneously, with the prospect of having to forfeit one should he win both.

But floating the possibility of becoming CSU leader while also campaigning for Commission president would raise doubts about whether Weber truly expects to win the EU's top post. The European Council has already said it is not legally bound to put forward a Spitzenkandidat as its nominee for Commission president. Many diplomats in Brussels are skeptical about whether Weber will become Commission chief, believing someone with more high-level political experience will end up in the position.

A source close to Weber said that despite speculation in the German media, Weber has never said that he wanted to be both Commission president and CSU leader, and is focused on his campaign for the top job in Brussels.

“The issue of the party chairmanship of the CSU is not on the table because Seehofer is elected until 2019,” the source said. “We are now going to Helsinki. Seehofer is coming there to support Weber to be EPP Spitzenkandidat. Weber is fully into Europe, EPP and Helsinki. He wants to lead the next Commission. That is what he is dealing with."