Known for tackling the major crises of her chancellorship, from Greece to Ukraine, with the detached sobriety of a scientist, the German leader is showing more emotion of late.
She cracks dark jokes about her own fate. For the first time, people in her entourage detect hints of exasperation and even self pity.
On Sunday, Merkel, 61, will mark the anniversary of a decade in office, a feat achieved by only two other post-war German chancellors, Helmut Kohl and Konrad Adenauer.
For much of those ten years, the pastor's daughter and former physicist has seemed like an indestructible political force. No matter what was thrown at her -- the global financial crisis, euro zone turmoil or Vladimir Putin -- she emerged stronger and more popular, at home and abroad.
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All that changed in a flash three months ago when the swelling stream of refugees fleeing war in the Middle East turned into a flood.
Merkel's reaction -- to suspend European Union asylum rules and welcome refugees into Germany with the message "Wir schaffen das" (we can do this) -- has been hailed as humane and politically courageous.
"She may have saved the European Union with her stance," says John Kornblum, a former US ambassador to Germany.
But as thousands of migrants continue to flow into Germany every day, stretching local communities to the limit, the feel-good glow of early September, when refugees were greeted with cheers at the Munich train station, has faded, replaced by frustration and, following last week's attacks in Paris, fear.
Support for Merkel's conservatives has slumped 5 points to 37 percent in just a few months, and a new party on the political right, the anti-immigrant Alternative for Germany (AfD), has surged.
Merkel's own popularity has also taken a big hit. In April, 75 percent of Germans thought she was doing a good job. In a survey by Infratest dimap last week, it was only 49 percent.
As she has sunk in the polls, the sniping from within her conservative ranks has grown louder.
Horst Seehofer, the head of her Bavarian sister party has turned into the chancellor's most outspoken critic. Lately, senior figures in her own party, from Finance Minister Wolfgang Schaeuble to Interior Minister Thomas de Maiziere, have joined in, pressing her for a tougher stance on refugees.
The open defiance has undermined Merkel's authority and left her looking more vulnerable than at any time since she took power in 2005, as the first woman and first politician from communist East Germany to lead the country.
No challengers
But calling the end of the Merkel era, as some in the German and international media have done, looks premature.
She faces no legitimate challengers on the right or left. And the rise of the AfD may actually make it easier for her party to win power in future elections by reducing the chance of leftist majorities.
More importantly, the German economy continues to purr along. Unemployment is hovering at its lowest level since reunification in 1990 and German finances are strong, with another balanced budget forecast this year despite rising costs linked to the refugees.
In the Infratest poll, 82 percent of Germans described the economic situation as good or very good.
"Of course declining poll numbers aren't nice but I'm not ready to say this is a catastrophe, that the world is about to end," Michael Fuchs, a senior lawmaker in Merkel's Christian Democratic Union (CDU), told Reuters.
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Still, giving Merkel the all clear seems just as premature given the complexity of the refugee challenge. Roughly 7,000 migrants are entering Germany every day and about a million are expected this year.
Merkel's closest aides say she has until the spring to show Germans that she can get the flow of migrants under control.
Three state elections in March - in Baden-Wuerttemberg, Rhineland Palatinate and Saxony-Anhalt - could prove decisive in determining whether Merkel runs for a fourth term or hands the baton to someone else after a 12-year run as chancellor.
The next federal election will be held in the fall of 2017.
"At this point I still think it's a near certainty that she runs. She definitely wants it," said one senior aide who requested anonymity.
"She will be measured on whether she can get a grip on the refugee crisis. Order needs to be restored, and order means a reduction in the numbers," said a second adviser. "This can't be done in the next weeks or months, but it needs to be achieved by the spring."
'Baffled'
Can Merkel get the numbers down by then? She has rebuffed calls from Seehofer and members of her own party to introduce a formal ceiling on the number of refugees Germany accepts, convinced that such a cap would be impossible to enforce.
But her alternative strategy - a five-pronged approach which foresees Turkey keeping more refugees; Greece and Italy erecting "hotspot" reception centres; EU partners accepting refugee quotas; Germany expelling migrants who are not granted asylum faster; and world powers working together to bring peace to Syria - is fraught with problems.
It leaves her uncomfortably dependent on leaders like Turkey's Tayyip Erdogan, Russia's Putin and Hungary's Viktor Orban. The attacks in Paris, may make the task even more difficult by deepening scepticism towards refugees at home.
"As macabre as it sounds, the attacks in Paris have provided Merkel with some political relief for now. And at the same time they have made everything more difficult," German newspaper Die Zeit said this week.
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That helps explain Merkel's rising frustration levels. Die Zeit described her as "unwavering" but increasingly "baffled" about how to solve the refugee dilemma.
In years past, critics accused Merkel of focusing obsessively on German interests and failing to see the bigger European picture.
But her clinching of a deal last summer to keep Greece in the euro zone, her tireless efforts to forge peace in Ukraine and her actions in the refugee crisis paint a different picture.
"If you talk about her legacy, the common thread is that she has kept Europe together under very difficult circumstances," said Kornblum, the former US ambassador.
"She used her leverage to keep the euro zone from breaking up, to keep Europe united on sanctions against Russia and lately to prevent a complete collapse over refugees."
But even her closest advisers worry that Merkel, regardless of how her own political fortunes play out over the course of 2016, may be reaching the limits of what she can do in Europe.
Looking across the bloc, they see a weakened French president, a British prime minister focused obsessively on his "Brexit" referendum and right-wing populist leaders in eastern Europe that are drifting away from Germany and the European mainstream.
"Merkel remains determined," the senior aide said. "The big worry is that Europe simply doesn't have the strength anymore."
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