Born in East Germany, she learned her political skills under Helmut Kohl who, with 16 years in office, holds the record for longevity among post-World War II German leaders.
A year ago, Merkel's chances of re-election were badly clouded by the Greek debt crisis.
As the EU's de facto paymaster, she had to negotiate a bailout to prevent other debt-ridden countries from collapse, a domino effect that would have destroyed the euro.
At the same time, she had to demand austerity from the Greeks to meet fears at home that German taxpayers would be left to pay for yet another "Club Med" basket case.
Today, the situation for Merkel is bonny. The euro-zone crisis - for now - is under control and has barely surfaced in the election campaign. Germany's economy is on the up, dulling criticism that flared when Merkel started an austerity drive after the implosion of the financial markets.
Polls published this week say Merkel's Christian Democratic Union (CDU) and its Bavarian ally the Christian Social Union (CSU) have about 40 per cent of the vote, about 15 points more than the Social Democrats.
The Free Democratic Party, which is in coalition with the CDU and CSU, has around 6 per cent.
The Greens, in alliance with the Social Democrats, are credited with about 13 per cent and "Linke" (Left), a far-left opposition group that does not have a partner, about 8 per cent. The eurosceptic Alternative for Germany, now strongly in retreat, would not get across the 5 per cent threshold entitling it to seats in the 622-member legislature.
Steinbrueck, 66, was selected by the Social Democrats for his reputation as the no-nonsense finance minister during a "left-right" coalition in Merkel's first term.
The party has lost 10 million voters in 15 years, a loss blamed mainly on poor economic management.
An able speaker but prone to gaffes and squabbles with other party heavyweights, Steinbrueck has been energetically doing the rounds, pounding out a message of social justice - a message Merkel has skilfully subverted by pinching the Social Democrats' idea of rent controls.
A recent cartoon in the daily Tagesspiegel has Steinbrueck frenziedly boxing at shadows while Merkel snoozes in a beach chair.
Steinbrueck's hopes in the final weeks lie on winning over voters who are undecided or apathetic. Nearly a quarter say they have no interest in the election, and CDU electors in particular have a history of not voting.
He is also counting on the support of the last Social Democratic chancellor, Gerhard Schroeder, who in 2005 whittled a Merkel lead of 13 points five weeks before the vote to a single point.
The risks of complacency were spelt out by Merkel's campaign manager, Hermann Groehe.
"Past experience tells us that good numbers in the opinion polls 50 days before the election are no guarantee of a good election result," he said this week.
