The Standard & Poor's decision to lower France's rating to AA+ was a blow to the country's self-image and to Sarkozy's prospects of re-election, coming just three months before the first round of voting.
It could also have far-reaching effects for Europe, potentially raising the borrowing costs for the bailout fund used to rescue struggling members of the eurozone. The move was one of a spate of downgrades of countries that use the euro that the agency said reflect the absence of a sufficiently bold political solution to the crisis.
The French president has kept mum about Friday's downgrade thus far, instead trotting out his finance minister and prime minister to respond to the move that had been widely expected.
While he also avoided any mention of the downgrade on Sunday, Sarkozy turned a speech to mark the 100th anniversary of the birth of a founding father of the current republic into a kind of campaign rally, while also trying to appear to be above the fray.
"This is a test and since it is, we have to confront it, we have to resist, we have to fight," Sarkozy told an audience in central France. "We have to demonstrate courage, we have to demonstrate calm."
Socialist presidential candidate Francois Hollande, who was topping the polls even before the downgrade, has said the move was a result of Sarkozy's failed policies.
"You don't respond to a crisis of this magnitude with agitation, outbursts and polemics," Sarkozy said Sunday by way of retort.
Sarkozy said France must show the courage to reform, and promised to unveil a set of "important decisions" before the end of the month — without giving any details — to confront the crisis.
His government was twice forced to make extra budget cuts last year to stay on track with a promise to balance the budget by 2016. Finance Minister Francois Baroin promised that even with the downgrade, no new cuts would be necessary.