German Chancellor Angela Merkel's party faces a first election-year test against resurgent leftwing challengers when voters go to the polls on Sunday in the tiny region of Saarland.
Although the state on the French border is home to just one million people, the poll there is seen as a first litmus test in the battle between Merkel and the Social Democrats under their new leader Martin Schulz.
The centre-left SPD -- having long languished in the shadow of the "Queen of Europe" -- has been gripped by almost giddy optimism under Schulz, 61, the folksy and plain-spoken former European Parliament president.
The SPD has gained around 10 points nationally since Schulz took over in January with a social justice platform and a bold vow to end Merkel's almost 12-year reign in September's general election.
The "Schulz mania" has particularly drawn younger voters to the workers' party, which is now neck-and-neck with Merkel's conservative bloc -- both nationally and in Saarland.
Even if the CDU comes out ahead in the region, the SPD could grab power if it teams up with the far-left Linke and possibly the ecologist Greens parties -- a so-called "red-red-green" coalition it is also flirting with nationally.
Merkel, 62, has warned local voters that "red-red or red-red-green experiments should be avoided" and urged them to stick with the CDU's "path of success".
Speaking at a campaign event there ahead of the vote Sunday, which also marks the change to summer time, she said "we don't want to turn back the clocks, we want to turn them forward".
She also cautioned, speaking before a 4,000-strong crowd, that a leftist coalition would harm the economy and "wall it in with taxes, bureaucracy and red tape", DPA news agency reported.
A starker warning came from the top candidate of the pro-business Free Democrats, Oliver Luksic, who cautioned against turning Saarland into a modern version of the former communist East Germany or "a GDR lite".
- 'We paid enough' -
While Merkel long seemed unbeatable at the ballot box, she has been weakened by a populist backlash against her decision to open German borders to refugees which has brought in a million asylum seekers since 2015.
This has boosted the anti-immigration Alternative for Germany party which, despite a recent dip in popularity, is still expected to enter the opposition benches of the 11th of Germany's 16 state assemblies on Sunday.
As the refugee crisis has abated, the campaign race is increasingly being fought along traditional ideological lines.
While Merkel broadly argues that Germany, the EU's top export engine, is prosperous and needs to stay competitive to keep it that way, Schulz points to the army of "working poor" and promises to narrow the wealth gap.
Saarland, though tiny, in some ways reflects the bigger economic challenges. The former coal region, where the last mine closed in 2012, has sought to establish itself as a research and IT hub.
It has been ruled by the CDU, alone or in coalition, since the mid-1950s except for the 1985-98 reign of former SPD premier Oskar Lafontaine.
Lafontaine -- who later defected to the Linke party -- has campaigned for a leftist coalition with posters that promise "We've paid enough -- now it's the turn of the rich".
A change of government was now "within reach" in Saarland, the 73-year-old said this week.
Polls predict a tight race between the two top candidates, both women.
One is CDU state premier Annegret Kramp-Karrenbauer, 54, often dubbed simply "AKK", who is considered pragmatic and unpretentious and likes to dress up as a cleaning lady at carnival festivities.
Her SPD challenger is AKK's current deputy in a grand coalition, Anke Rehlinger, 40, who happens to hold the state record in shot put (16.03 metres).
The latest Insa poll for Bild newspaper gave the CDU a narrow 33-35 percent lead over the SPD, while the Social Democrats' potential ally the Linke scored 13 percent.
A victory for a leftist alliance in Saarland would "send a signal," said news weekly Der Spiegel. "And it would make red-red-green more likely at the national level."