Only days after the Commission president handed over his political programme ahead of a key Parliament hearings this week, Fillon's candidature re-emerged as a possibility should Barroso's bid fail.
An unnamed French minister cited by French daily Le Monde on Monday (7 September) said French Prime Minister François Fillon was "hedging its bets on the hypothesis of a failure of Barroso".
The minister admitted the idea had "low probability" of materialising, but nevertheless said it was "not stupid" to consider it.
According to the source, Fillon's candidacy could gain momentum if Barroso were rejected by Parliament or if a second rejection of the Lisbon Treaty in Ireland were to unleash renewed calls for radical change at the head of the EU executive.
The political groups in the European Parliament are due to grill Mr Barroso during behind-closed-doors hearings tomorrow and Wednesday (8-9 September). The Greens and leftists are the only groups so far to have openly rejected the Portuguese.
A plenary vote over Barroso's re-appointment is to be staged at a later date, tentatively set for 16 September.
"Everybody is entitled to speculate," said Commission spokesperson Johannes Laitenberger during a regular media briefing today (7 September), adding that this was "part of political realities".
Laitenberger said Barroso was "not really worried" about such speculation at the moment, adding that he was "busy preparing his meetings with political groups in Parliament".
"President Barroso is the only candidate which has been approved unanimously by the 27 heads of state," the spokesperson reminded journalists.
Fillon's interest in the European Commission job already made headlines in March this year. His name was mentioned in a book by Jean-Pierre Jouyet, a former secretary of state for European affairs who is a close ally of French President Nicolas Sarkozy.
Fillon's candidacy is supported by Daniel Cohn-Bendit, co-president of the Green group in the European Parliament, who are Barroso's staunchest opponents.
