The European Commission has appointed Justice Commissioner Didier Reynders to take the reins on competition issues after the current chief, Magrethe Vestager, temporarily stepped down on Tuesday.
Ms Vestager, a commission executive vice president, announced on X, formerly Twitter, that she would take a temporary leave of absence as “I am officially a candidate for the presidency of the European Investment Bank”.
Under EU rules, that means she must step away from her commission duties until it is decided whether she will get the job at the bloc's lending arm.
The commission said in a statement that Mr Reynders would take on the competition portfolio and report directly EU Commission President Ursula von der Leyen.
Ms Vestager's other commission duty as the executive vice president steering Europe towards a digital future will be taken up by Vera Jourova, who already serves as executive vice president for values and transparency.
If she is unsuccessful in nabbing the top job at the EIB, Ms Vestager will be able to return to her commission role.
If she does get the post, Ms von der Leyen would have to appoint a candidate from Ms Vestager's home country of Denmark under rules requiring representation across the 27-nation bloc.
Ms Von der Leyen “has granted unpaid leave to Executive Vice President Vestager underlining that during that period the relevant provisions of the Treaties and the Code of Conduct for the members of the commission continue to apply”, a statement said.
It added that the European Parliament and the European Council, which represents the member states, were being informed.
Ms Vestager had been a critical force in the past against US-dominated Big Tech, hitting the world's technology behemoths with investigations and heavy fines.
Her star has waned in recent years, though, after a series of setbacks, with losses in top EU courts against some of the biggest companies including Amazon and Apple.
She has been a long-time favourite for the EIB role but the race became tighter after the Spanish government put forward Economy Minister Nadia Calvino for the position.
EU finance ministers are expected to agree on a name at their next meeting in Spain later this month.
Werner Hoyer is the current EIB chief and is set to leave the post by the end of 2023.
Ms Von der Leyen's commission is nearing the end of its five-year term, with EU elections in June 2024 to lead to the formation of a new EU executive.
Another commission vice president, Frans Timmermans, resigned two weeks ago to stand in general elections in his native Netherlands, with ambitions of becoming that country's next prime minister.