Remarkably for a French president, Sarkozy has now gone out of his way to sing the praises of Germany's economic system, extolling its pragmatic reforms of labour law and lower payroll charges.
"The time when he would privately call the chancellor 'fatso' and the Germans 'the Boche' is long gone," the conservative German daily, the Sueddeutsche Zeitung, commented sardonically. "He has now hitched his fate to 'dear Angela' and the 'German model'."
And, in a move that has no precedent in French political history, Merkel has waded into France's presidential election campaign on Sarkozy's behalf.
Voting is now less than 80 days away and he is still not officially a candidate. But Merkel this week declared her backing for a second Sarkozy term. "I support Nicolas Sarkozy on all levels because we belong to political parties which are friends," Merkel said in a TV interview with Sarkozy. "We belong to the same political family. He supported me [in Germany's 2009 elections] and it is natural that I support him in his campaign."
Sarkozy thanked Merkel for her "friendship and trust".
"When someone for whom you have affection and whom you admire says 'I back your actions', that pleases me," he said, but added: "The French people, like the Germans, will decide for themselves, freely."
Merkel's office said her support for Sarkozy's re-election was as head of Germany's Christian Democratic Union, not as chancellor.
But some of her aides are even suggesting she will join him on the campaign trail ahead of the first round of voting on April 22.
A run-off vote will be held on May 6 if no candidate picks up more than half of ballots cast.
Merkel's endorsement is causing clear unease within Sarkozy's UMP party. Part of this is because of xenophobia among right-wing voters, who are being courted powerfully by Marine Le Pen, head of the National Front. Yet there is also a strand of nationalism that can be found in all the mainstream parties.
Then there is the question of Merkel herself. Even though she is a moderate conservative and a committed European, she is being attacked in Italy and Greece as arrogant or dogmatic, a fiscal puritan wielding Germany's whip.
"We must be careful not to appear to be following Germany's lead," said Lionnel Luca, a UMP politician, who warned of "the whiff of Germanophobia".
Henri Guaino, who as special adviser to the President is Sarkozy's right-hand man, said he was "cautious" about the idea that Merkel could make campaign appearances.
"When Mrs Merkel says how much her relationship with President Sarkozy is good, constructive and fruitful, I only see good things," Guaino told Europe 1 radio station.
"Now, the French presidential election is the affair of the French public, just as the German elections are the affair of the Germans."
Sarkozy's opponent, socialist candidate Francois Hollande, dismissed Merkel's help for Sarkozy, saying: "I don't need the support of anyone but the votes of the French people."
For Merkel, the alarm bells rang weeks ago when Hollande, pushing a 1970s-style tax-and-spend agenda, declared he would tear up the fiscal pact for budgetary austerity that she views as essential for saving the euro.
Polls say Hollande would take 28-30 per cent of votes in the first round, against 23-24 per cent for Sarkozy, and win convincingly if the two were paired in the run-off.