Berlin: German Chancellor Angela Merkel attacked her Social Democratic challenger as a spendthrift as both sides concluded an increasingly testy campaign for the biggest and last state election before the national vote in September.

More than a fifth of the nation’s electorate is in play on Sunday in North Rhine-Westphalia, making the industrial region of 18 million people a key indicator of the national mood as Merkel seeks a fourth term in the fall. Polls suggest the race between the state’s SPD premier, Hannelore Kraft, and Merkel’s Christian Democratic candidate is too close to call.

With Martin Schulz under pressure to keep his Social Democrats in contention for the chancellery, Merkel took aim at her main opponent’s calls for expanded social programs at a rally in his home city of Aachen.

“The SPD candidate in the federal election has it backward: he talks a lot about justice, and then maybe about innovation as an afterthought,” Merkel told supporters Saturday on a square near Aachen’s medieval cathedral. That approach leads to debt on the backs of future generations, she said.

Kraft, the state leader who’s the SPD’s line of defence against another setback for Schulz, accused Merkel of exaggerating the region’s struggles with crime, government spending and its notorious traffic jams.

“It’s indecent to badmouth this state, and I include the CDU chairwoman in this regard,” German Foreign Minister Sigmar Gabriel, one the most senior Social Democrats in Merkel’s cabinet, said at the same SPD rally in the steel city of Duisburg on Friday. Merkel, in office since 2005, has also headed her Christian Democratic Union since 2000.

Written off last year for her refugee stance, Merkel is rebounding after the SPD’s “Schulz effect,” a poll surge following his nomination in January, tapered off. It’s raising the stakes for the SPD after two consecutive state defeats by the Christian Democratic Union, including an election last Sunday in Schleswig-Holstein, where the CDU unseated a Social Democrat-led government.

That landed a blow to Schulz, a former European Parliament president, who generated hope among Social Democrats that he could pose the most serious threat yet to Merkel.

A victory for Merkel’s party in North Rhine-Westphalia, where Social Democrats have governed for 45 of the last 50 years, would consolidate her advantage ahead of the national vote on Sept. 24. The chancellor is promoting herself to German voters as a steady hand as Europe is buffeted by political risk, including a resurgent Russia under Vladimir Putin and an unpredictable ally in US President Donald Trump.

All polls in the state point to losses for the governing SPD and Greens, suggesting their coalition government won’t get another term. The CDU had 32 per cent support compared with the SPD’s 31 per cent, according to the latest FG Wahlen poll for broadcaster ZDF.

Merkel and Schulz criss-crossed the region for weeks, with Schulz seeking to maintain support for his message of social justice in a state that’s lost the leverage it once had with its industrial might. Merkel has hit hard on the SPD’s record on crime and debt, rallying a CDU base that traditionally has a difficult time getting the upper hand.

“The SPD is very nervous right now,” Armin Laschet, the CDU candidate for state premier, told a rally with the chancellor in the town of Haltern am See on Wednesday.

National polls have also shifted against the SPD since some surveys showed Schulz lifting his party to parity in February and March. Support for Merkel’s CDU-led bloc rose 2 percentage points to 37 per cent and the SPD declined 3 points to 27 per cent compared with late April in an Infratest Dimap poll published Thursday.