Germany's Political Parties at a Glance

Berlin: German voters will head to the polls for a general election on September 24, with surveys giving Chancellor Angela Merkel's conservatives a double-digit lead over their closest rivals, the Social Democrats.

But the race for third place is wide open, and in Germany's coalition system the smaller parties could tip the balance of power.

Here's a look at the parties expected to clear the five percent threshold to enter parliament.

The heavyweights

-- CDU: Founded after World War II, the centre-right Christian Democratic Union is the main conservative party, popular with the upper middle class and professionals.

Under Merkel, it has moved closer to the centre by adopting more leftist policies such as ending army conscription, scrapping nuclear power and opening the country's borders to refugees.

The party has shown loyalty to Merkel, in power for 12 years, but with no clear successor in sight critics have accused it of failing to prepare for the future.

-- CSU: The Christian Social Union is the CDU's more conservative sister party in the wealthy, staunchly traditional state of Bavaria. Its pugnacious leader Horst Seehofer was one of the loudest critics of Merkel's decision to take in hundreds of thousands of asylum seekers in 2015.

The CSU aligns itself with the CDU at a national level. Together, they have been the leading partnersin most of Germany's post-war governments.

-- SPD: Germany's oldest party at more than 150 years old, the Social Democratic Party is the natural home of the working class and the country's powerful unions.

Supporters accused it of betrayal when an SPD-led government forced through punishing labour reforms at the start of this century. Those reforms have since been credited with helping Germany's economic boom.

The SPD has struggled to shine as the junior partner in Merkel's grand coalition these past four years, despite pushing through a minimum wage, gay marriage and measures for more equality in the workplace.

Hopes that new SPD chief Martin Schulz can turn the tide and replace Merkel as chancellor have fizzled out along with his brief surge in the polls.

Possible kingmakers

-- FDP: The pro-business Free Democratic Party stands for liberal values, espousing free market capitalism and individual freedoms. It has spent more time in government than any other party, always as the junior partner to either the CDU/CSU or the SPD.

But after a lacklustre stint governing in Merkel's shadow, it humiliatingly crashed out of the Bundestag in the last election.

The FDP is now hoping for a comeback under telegenic young leader Christian Lindner, although critics say the party's platform is too vague.

-- The Greens: With its roots in the 1970s pacifist, anti-nuclear movement, the Greens played a pioneering role in advocating for gay rights and the shift away from nuclear energy.

But the Greens have struggled to keep voters energised as their core issues have gone mainstream.

Currently polling in the single digits, some commentators predict the Greens will have to choose between staying in opposition or joining a Merkel-led government that could also include the FDP, dubbed a "Jamaica coalition" after each party's colours and the Caribbean country's flag.

Opposition voices

-- Die Linke: Founded by communists from former East Germany and SPD defectors, the fiercely pacifist, anti-corporate far-left Die Linke is Germany's main opposition party.

Despite making it into several regional governments, its radical demands for the dissolution of NATO and the end of German military deployments abroad mean it is an unlikely coalition member at national level.

-- AfD: The Alternative for Germany began life in 2013 as a eurosceptic party before morphing into an anti-Islam, anti-immigration outfit. After capitalising on widespread anger over Merkel's refugee influx, the right-wing populists won seats in 13 of Germany's 16 state parliaments.

But endless infighting and a recent slowdown in asylum arrivals have sapped support for the party. Nevertheless, it remains on track to enter the national parliament for the first time. Shunned by other parties, the AfD would be headed straight for the opposition benches.