The prime-time clash was supposed to be Social Democrat (SPD) leader Martin Schulz's last chance to sway millions to his cause but the general consensus among media commentators is that he failed.
Merkel still has a commanding 17 percentage point lead over her SPD rival.
There were high hopes in the centre-left party's ranks that its candidate could beat Merkel when Schulz, the former head of the European Parliament, announced his candidacy earlier this year.
But his campaign has failed to turn the tables on Merkel's Christian Democrats (CDU), with whom his party has been in a coalition government since the last election.
"He has two main difficulties, the first one bieng that people like Angela Merkel," Marcel Dirsus, a political scientist at the University of Kiel, told RFI. "That's quite tough when you are in the opposition.
"The second problem that he faces is that Angela Markel is very experienced. You see a world in turmoil and when people see that they want to go for her."
What makes Merkel so popular ?
Economic prosperity and stability in a troubled world make up Merkel's magic formula, analysts say.
"Her slogan is 'For a Germany where we like to live well and we live well', it doesn't mean anything but ''Give me another mandate for four years and you won't be bothered by politics and prosperity will continue," explains Thorsten Benner, the head of the Global Public Policy Institute in Berlin. "That's her promise and she's done a pretty decent job. She promises continuity and that's what part of the electorate wants."
Far right's support slumps
According to the latest opinion polls, Merkel's CDU would come first at around 39 percent, while Schulz's SPD would make it to second place, with only 22 percent.
The hard-left Die Linke is given 10 percent, the Greens, the liberal FDP and the far-right party AfD are all predicted to win eight percent.
The AfD, which had capitalised on the arrival of two million refugees in the country in 2015, was credited with almost 20 percent a year ago.
"It would be the first time that a quasi-fasict party enters the parliament since the Nazis were brought out of power," says Thorsten Benner. "10 percent, for a French person that does not seem like a lot but for Germany it's quite a new thing."
While in Germany no one doubts Merkel's fourth victory, she will probably fall short of a majority and will have to form a coalition, as she has had to do before.
"The way that the German system works is that you almost always have a coalition," says Marcel Dirsus. "You try to find a coalition that works best for your base. The most natural option would be the FDP, the pro-business liberals, and I think that would the Angela Merkel's prefered option. But it remains to be seen if they have enough votes."
Voting will take place on the 23 September and, while Merkel's victory might not be the most thrilling news story of the year, it will please other European governments, which, exhausted by populism, Donald Trump and Brexit, are looking for stability in the EU's biggest member state.