Tight races for power -- each with their own unique electoral dynamics -- are expected in the city-state of Berlin and the northeastern state of Mecklenburg-Western Pomerania.

The Alternative for Germany is expected to make strong gains in both, a fortnight after it trounced Merz's center-right CDU by a margin of almost 44 to 17 percent in the ex-communist eastern state of Saxony-Anhalt.

The AfD triumph badly rattled Merz and fueled speculation that the 70-year-old leader, who took power in May last year, may not sit out the end of his four-year term as leader of Europe's top economy.

Amid speculation about a potential change at the top, eight CDU state premiers closed ranks Wednesday and declared jointly that Germany needs "stability now more than ever" rather than "discussions about personnel".

Merz has vowed to reboot Germany's flagging economy, rearm the country to deter a hostile Russia and contain irregular immigration to soothe voters' fears and lure them away from the AfD.

Instead, the AfD now leads nationwide polls, Merz's personal approval ratings hover around 10 percent, and his coalition with the center-left SPD is increasingly torn by infighting.

"In Merz's case, we are now observing the possibility of a tipping point -- an implosion rather than a slow erosion of authority," said Oliver Lembcke, a political scientist at Ruhr University Bochum.

"When election defeats, poor personal ratings and internal party doubts reinforce one another, political authority can collapse very quickly."

Two close election battles

In one election Sunday, in Mecklenburg-Western Pomerania, Merz's party is an onlooker to the main battle between the SPD of popular state premier Manuela Schwesig and the AfD.

While the AfD was polling at 37 percent against the SPD's 35 in the latest INSA survey, Merz's CDU, at just seven percent, may drop dangerously close to the five-per cent hurdle needed to stay in the state parliament.

A CDU crash below that line would be a historic first and heap enormous pressure on Merz.

If the CDU "were indeed to fail to clear the five-percent threshold, I consider it quite likely that Mr Merz would be pressured by his party to step down," said Ursula Muench of the Academy for Political Education in Tutzing. 

"Barring such a drastic turning point, I do not foresee this happening for the time being." 

In Berlin, the ruling CDU is running a neck-and-neck race against the far-left Die Linke, which is popular with many young people and promises drastic steps to solve a dire housing crisis.

A CDU defeat in the capital would be another black eye for Merz.

The AfD is meanwhile expected also to do well in Berlin, although it is set to remain shut out of power in both states because all other main parties have agreed on a "firewall" of non-cooperation with it.

'Dissatisfaction running high' 

Whoever wins either poll, the AfD is sure to again channel voter discontent with the mainstream parties.

"I do hope they vote for the AfD here; I can tell you, because the CDU have been in power for years and they haven't got their act together," said Berlin retiree Manuela Schmidt, 63.

She pointed to poverty-stricken pensioners collecting bottles off the streets to collect the deposits.

"They've worked for 45 years, get a pension of 500-something (euros per month), and go out at night to collect bottles, only to be driven away by foreigners in the end ... and that simply can't go on," Schmidt told AFP.

Merz -- bracing for a tough Sunday evening -- has scheduled a CDU executive committee meeting then to quickly discuss the election results and the way forward.

He also cleared his calendar for the coming week by scrapping plans to travel to the UN General Assembly, sending his foreign minister to New York instead.

"Dissatisfaction is evidently running high" in the CDU camp, said Muench, adding, however, that cooler heads might eventually prevail to avoid boosting the AfD under co-leader Alice Weidel.

"It must surely be clear to level-headed CDU politicians that replacing the CDU chairman and chancellor would not serve their own interests," she said. "It would just fuel the AfD's pipe dreams of a 'Chancellor Alice Weidel'."

Berlin elects a new mayor

Voters in Germany's capital will elect a new local parliament, with the winning party set to take first crack at forming a coalition to put forward Berlin's next mayor.

The vote in long-divided Berlin is being closely watched for its wider impact on national politics. Here are the five key figures:

 Elif Eralp: far left eyeing power. The lead candidate for the far-left Die Linke, Eralp has campaigned against high rents in Berlin and made a controversial vow to expropriate apartment buildings owned by large corporate landlords.

That has struck a chord, putting Die Linke -- which traces its roots in part to the former East German communist regime -- ahead in some polls and on the threshold of power for the first time.

Die Linke has long been strongest in the former East Berlin but has also made gains among young voters and in immigrant neighbourhoods.

If Eralp's party finishes first, she will likely try to forge a left-wing coalition with the Greens and Social Democrats (SPD).

Born in Munich to Turkish trade unionists who had fled their home country, the 45-year-old Eralp would be Berlin's first mayor with immigrant roots.

She worked as a lawyer advocating for immigrants and against racism before turning to politics.

Eralp is sometimes compared to Zohran Mamdani, the charismatic left-wing outsider who became mayor of New York.

Like his party, Die Linke has faced allegations of antisemitism over a dominant pro-Palestinian stance -- which is at odds with the strongly pro-Israeli position of most mainstream parties in Germany.

 Stefan Evers: proudly conservative. Berlin's outgoing mayor, Kai Wegner, was ditched by his centre-right CDU party late in the campaign amid a long-running scandal over his handling of a mid-winter blackout in the city.

The Christian Democrats instead tapped Stefan Evers, the city's current finance chief, as their standard bearer.

Evers has the CDU running neck-and-neck with Die Linke, with recent polls putting both at around 20 percent, though that would mark a considerable decline for the conservatives.

Evers, 46, who usually sports a sober suit and thin-framed glasses, has run an understated campaign that reflects the party's buttoned-down and businesslike positions.

Evers's track record includes painful budget cuts for the debt-ridden city. 

"Someone has to be sensible," reads one campaign poster for Evers, who hails from western Germany and calls himself "conservative and proud of it".

To become mayor, he would likely have to form a tricky three-way coalition with the SPD and Greens.

Kristin Brinker: far right challenger. The AfD hopes to pull off an upset and take the lead in Berlin, just two weeks after its resounding success in Saxony-Anhalt state.

It has been polling at around 18 percent, double the result last time, under lead candidate Kristin Brinker, an architect who has campaigned on concerns over crime and immigration.

The AfD is strongest in Berlin's outer east, an area largely dominated by communist-era prefabricated housing blocks.

Brinker told AFP she would prioritise "local people" -- those "who have lived here the longest" -- for affordable social housing.

She, however, has no chance of becoming mayor, since no other party would consider a coalition with the far right. 

Werner Graf: classic Green. Berlin's Greens are polling at 16 percent under lead candidate Werner Graf, who advocates more housing construction and classic Green issues like better bicycle lanes and public transport.

The Greens have built a strong base in the city's trendy central districts.

Graf, who speaks with the distinct accent of his native Bavaria, could become a kingmaker as his party may prove decisive in securing a governing majority for either Eralp or Evers.

 Steffen Krach: Social Democrats crashing? The SPD ruled Berlin for more than two decades before being knocked from power in 2023 and ending up the junior partner in an awkward coalition with Wegner's conservative CDU.

They have now pinned their comeback hopes on Steffen Krach, who until recently was a top political leader of the western city of Hanover.

Krach had previously worked in Berlin city government and was seen as a relatively young and charismatic new face for the party. 

But a potential disaster looms, with the SPD polling at just 12 percent -- and Krach the subject of an investigation into financial irregularities regarding a public contract back in Hanover, something he denies.

While the SPD could join in a left-wing coalition, Krach has come out firmly against Die Linke's plans to expropriate real estate firms.

In Mecklenburg-Western Pomerania, the premier hopes to halt far-right surge

Germany's anti-immigration AfD party is eyeing another election triumph on Sunday in a northeastern coastal state where the popular premier is campaigning on a promise to hold back a rising far-right tide.

Manuela Schwesig of the center-left SPD -- a cancer survivor with high personal approval ratings and a large social media following -- is fighting a battle that is being closely watched, especially in the office of Chancellor Friedrich Merz. 

The race in Mecklenburg-Western Pomerania pits her against Leif-Erik Holm, a former radio host who threw in his lot with the pro-Donald Trump and Moscow-friendly AfD.

Holm, 56, is not known for the radical edge or charisma of some other AfD figures but could still ride the far-right party's momentum.

"The race here is very clear," Schwesig, 52, who hopes to keep governing with a leftist multi-party coalition, told AFP during a campaign stop in the Baltic Sea port of Rostock.

"Either the AfD becomes the strongest force, or the SPD remains the strongest force."

Merz's center-right CDU is almost a bystander in the two-corner bout -- but still has everything to lose.

While the AfD was polling at 37 percent against the SPD's 35 percent in the latest Bild daily INSA survey, Merz's CDU, at just seven percent, may drop dangerously close to the five-per cent hurdle needed to stay in the state parliament.

A CDU crash below that line would be a historic first and heap pressure on Merz as leader.

As such, all eyes have been on Schwesig, a former national family minister whose motto has been the "Frau gegen Blau" -- the woman against blue, the AfD's signature colour.

Once trailing badly in the polls, the SPD has narrowed the gap in recent weeks, raising its hopes of scoring a last-minute victory as it hopes to build another coalition government in the sparsely populated state.

"We are fighting for democracy," said one of Schwesig's supporters, Daniel Prokof, 40. "The most important thing is simply that the AfD does not come to power here."

To defend the political centre, Schwesig has attacked it at times.

Seeking to insulate herself from voter anger at Berlin, she has publicly challenged the national government on its plans to tighten pension rules and over soaring fuel prices.

The AfD rallied around Holm last weekend in the small lakeside town of Buetzow.

Holm and other AfD politicians had to compete with loud punk rock music from anti-AfD protesters, who faced off across the town square with young men with close-cropped hair and black combat boots.

Some in the pro-AfD crowd expressed eager support for the party's promise of mass "remigration".