Although Germany's multicultural hipster capital looks bound to re-elect the centre-left Social Democrats (SPD) as the top party, the AfD is polling at around 14 percent with support strongest in the poorer tower-block districts of the city's former communist east.
This would place the anti-migrant Alternative for Germany into its 10th of the country's 16 state assemblies, a year ahead of national elections, and continue a voter drift away from the mainstream parties.
Breaking a taboo in post-war German politics, the AfD openly panders to xenophobic and anti-Islam sentiments, similar to France's National Front or far-right populists in Austria and the Netherlands.
It has also tapped into popular frustration with the two major parties who - from Berlin's glass-domed Reichstag building - rule Germany in a right-left 'grand coalition' with a crushing majority.
One member of Merkel's centre-right Christian Democrats (CDU) who said he plans to defect to the AfD is Bastian Behrens, a 42-year-old public relations executive from Berlin's leafy southwest.
At an AfD meeting he charged that, of the one million asylum seekers who came to Germany last year, many are "economic refugees".
"It costs a lot of money and it's hard to integrate them - just look at the Turks who came here 30 years ago," he said, pointing to western Berlin's large ethnic Turkish community.
"Many of them haven't integrated," he claimed. "They form a parallel society."
'Big party losses'
Political scientist Nils Diederich of Berlin's Free University said that, since the SPD in Berlin has traditionally beaten the CDU, its current junior coalition partner in the capital, the outcome will have little meaning nationwide.
The real issue, he said, will be "the size of the losses of the big parties to the AfD".
"I think, in Berlin too, the AfD will mobilise people who normally don't vote, and people who have conservative right-wing views but have so far been unwilling to vote for right-wing extremists."
More than 70,000 asylum seekers came to Berlin last year, with thousands still housed in refugee shelters, including the cavernous hangars of the Nazi-built former Tempelhof airport, once the hub for the Cold War-era Berlin airlift.
The migrant issue looms large, but it isn't the only election topic in the city of 3.5 million people.
Affordable housing has become a hot-button issue as property prices and rents have shot up with an influx of 50,000 newcomers every year, though they are still far below the costs in Paris and London.
Berlin - though a European metropolis loved for its arts scene, green spaces and vibrant nightlife - is also chronically broke and suffers an above-average jobless rate of around 10 percent.
Lacking major industry, it is a net beneficiary of public funds transferred from rich states such as Bavaria, although it prides itself on a growing IT start-up scene and tourism.
The city's understaffed administration is notorious for its long waiting times, exemplified by chaotic scenes at its Lageso migrant registration centre last year.
Another symbol of Berlin's often disastrous planning is a huge, empty airport complex, the opening of which has run years behind schedule and is now pencilled in for late 2017.
'Poor but sexy'
The airport was planned in the era of colourful former SPD mayor Klaus Wowereit, a popular and openly gay bon vivant who coined the Berlin motto "poor but sexy".
His successor, the far blander Michael Müller, 51, is now battling for a popular mandate, having taken over mid-term from Wowereit almost two years ago.
His main opponent is the CDU's Frank Henkel, 52, who is running on a law-and-order platform, having ordered mass police raids targeting anti-capitalist squatters and demanded equipping police with tasers.
Müller's SPD, which has ruled west and then reunited Berlin alone or in coalition for most of the past few decades, looks set to again emerge as the strongest party, polling at 24 percent in a survey for public broadcaster ZDF.
This puts it easily ahead of the CDU, which scored 19 percent, and other parties such as the Greens and the far-left Linke.
Still, it would be the SPD's worst result in years and likely force it to rule in a three-way leftist coalition, given the increasingly frayed political party spectrum.