She was called "the leader of the free world" as authoritarian populists were on the march in Europe and the United States, but Angela Merkel is wrapping up a historic 16 years in power with an uncertain legacy at home and abroad.

In office so long she was dubbed Germany's "eternal chancellor", Merkel, 67, leaves with her popularity so resilient she would likely have won a record fifth term had she sought it.

Instead, Merkel will pass the baton as the first German chancellor to step down entirely by choice, with a whole generation of voters never knowing another person at the top.

Her supporters say she provided steady, pragmatic leadership through countless global crises as a moderate and unifying figure.

Yet critics argue a muddle-through style of leadership, pegged to the broadest possible consensus, lacked the bold vision to prepare Europe and its top economy for the coming decades.

What is certain is that she leaves behind a fractured political landscape. It is also because of the long shadow she casts that her party's candidate, Armin Laschet, has struggled to sharpen his own profile.

His Social Democratic opponent, Finance Minister Olaf Scholz, has actively -- and perhaps successfully -- sold himself as the real continuity candidate.

Assuming she stays on to hand over power, Merkel will tie or exceed Helmut Kohl's longevity record for a post-war leader, depending on how long the upcoming coalition negotiations drag on.

- 'Do the right thing' -

The unflappable Merkel has served for many in recent years as a welcome counterbalance to the big, brash men of global politics, from Donald Trump to Vladimir Putin.

A Pew Research Center poll this week showed large majorities in most democracies around the globe having "confidence in Merkel to do the right thing in world affairs".

However, the last days of her tenure have also been marred by what Merkel called the "bitter, dramatic and terrible" return to power of the Taliban in Afghanistan -- a debacle in which she shares the blame as Germany completed its evacuation.

A trained quantum chemist raised behind the Iron Curtain, Merkel has long been in sync with her change-averse electorate as a guarantor of stability.

Her major policy shifts reflected the wishes of large German majorities -- among them phasing out nuclear power after the 2011 Fukushima disaster -- and attracted a broad new coalition of women and urban voters to the once arch-conservative CDU.

- 'Austerity queen' -

Before the coronavirus pandemic, her boldest move -- keeping open German borders in 2015 to more than one million asylum seekers -- seemed set to determine her legacy.

But while many Germans rallied to Merkel's "We can do it" cry, the move also emboldened an anti-migrant party, Alternative for Germany (AfD), ushering a far-right bloc into parliament for the first time since World War II.

At the same time, hardline leaders such as Hungary's Viktor Orban accused her of "moral imperialism" with her welcoming stance.

Six years on, she lamented this month, the European Union appears no closer to a unified policy on migration.

The woman once known as the "climate chancellor" for pushing renewables also faces a mass movement of young activists arguing she has failed to face up to the climate emergency, with Germany not even meeting its own emissions reduction commitments.

Merkel became Europe's go-to leader during the eurozone crisis when Berlin championed swinging spending cuts in return for international bailout loans for debt-mired countries.

Angry protesters dubbed her Europe's "austerity queen" and caricatured her in Nazi garb, while defenders credit her with holding the currency union together. 

More recently, despite admitted missteps in the coronavirus pandemic including a sluggish vaccine roll-out, Germany's death toll has remained lower than those of many European partners relative to population. 

- Kohl's 'girl' to 'Mummy' -

Merkel, the EU's and G7's most senior leader, started as a contemporary of George W. Bush, Tony Blair and Jacques Chirac when she became Germany's youngest and first female chancellor in 2005.

She was born Angela Dorothea Kasner on July 17, 1954 in the port city of Hamburg, the daughter of a Lutheran clergyman and a schoolteacher.

Her father moved the family to a small-town parish in the communist East at a time when tens of thousands were headed the other way.

She excelled in mathematics and Russian, which has helped her maintain the dialogue with the other veteran on the world stage, Russia's Putin, who was a KGB officer in Dresden when the Berlin Wall fell in 1989.

Merkel kept the name of her first husband, whom she married in 1977 and divorced five years later.

After the fall of the wall, Merkel, who was working in a chemistry lab, joined a pro-democracy group that would merge with Kohl's Christian Democrats.

The Protestant from the East whom Kohl nicknamed his "girl" would later be elected leader of a party until then dominated by western Catholic patriarchs.

As she rose to power, party rivals sneeringly called her "Mutti" (Mummy) behind her back but she deftly -- some said ruthlessly -- eliminated potential challengers.

Although her name has come up on wish lists for key EU or United Nations posts, Merkel has said she will leave politics altogether.

Asked on her final trip to Washington in June what she looked forward to most, she replied "not having to constantly make decisions".