As he arrived for the summit, Macron insisted he did not want to talk about possible names for the job -- before listing centre-left pick Frans Timmermans, EU Brexit negotiator Michel Barnier and EU Competition Commissioner Margrethe Vestager as suitable candidates, and pointedly omitting Weber.
'Credibility and know-how'
After the challenges of recent years -- which have seen the EU weather the migrant crisis and the Brexit earthquake -- Macron said the bloc needed someone to lead a "renewal".
The new commission leader must fully believe in this renewal "and have the experience to achieve it," Macron said.
"Because these are serious responsibilities at the European level which require experience -- whether in their own country or in Europe -- to have credibility and know-how," Macron said.
The repeated references to experience and credibility will be seen as a dig at Weber, who is seen as virtually unknown beyond the European Parliament, where he has spent the last 15 years.
An EU source said Weber could also seek the presidency of the European Parliament if he fails in his Commission bid -- a consolation prize not open to Vestager or Timmermans.
Under EU treaty law, the European Council of 28 national leaders nominates a commission president, then the new 751-member parliament ratifies their choice.
But the procedure, while seemingly straightforward, masks a complex power struggle between rival states and ideological blocs and between the leaders and parliament itself.
Former Dutch minister Timmermans has compared the ruthless intrigue to "Game of Thrones", and in the run-up to Tuesday's dinner, party and national leaders met in smaller groups to plot their strategies.
Many in Brussels argue that the European project is best served by a "political commission" headed by a president with a mandate from the parliament.
But most national leaders think the union's legitimacy derives from its member states and that the Council should be able to pick one of their own -- someone with leadership experience.
The EU elections saw the Liberal ALDE bloc and the Greensgain ground -- breaking the conservative EPP and centre-left S&D groups' ability to form a coalition majority without their cooperation.
'Pale and stale'
Momentum from the results is emboldening some liberals to push their candidate Vestager, with Luxembourg Prime Minister Xavier Bettel saying she would be "excellent".
As a woman, Vestager would help the Commission shed its "male, pale and stale" image -- there has never been a female president -- and she has a certain public profile after taking on the US internet giants as a regulator.
But she comes from Denmark -- a non-core member which opted out of the euro and the Schengen passport-free zone -- and may not have her home government's backing.
Vestager said it was "very, very difficult" to judge her chances of landing the job.
"If you can tell me what will happen every step from now, maybe, but everything is very opaque and very tricky," she said.
Timmermans, a centre-left Dutchman with more executive experience, will have the S&D's backing and ALDE, while dubious about the process, could back Margrethe Vestager.
Another option might be Barnier, an EPP member and the EU's chief Brexit negotiator, who did not run as a candidate but has been waiting in the wings, ready to step forward.