A defeat could leave Schröder's ruling coalition in tatters 16 months ahead of Germany's next general election.

The Social Democratic Party (SPD) has ruled Germany's most populous state for 39 years, but the 13 million voters in the industrial heartland look almost certain to choose the opposition Christian Democratic Union (CDU), completing a miserable set of state elections for Schröder.

In 1999, the SPD governed in 11 of Germany's 16 regions but if it loses on Sunday it will be in charge of only five.

Wide margin

The margin of the opposition's victory could be as great as 10 percent, setting a demoralizing tone for the ruling coalition.

In a possible sign of the SPD's growing desperation, Spanish Prime Minister Jose Luis Rodriguez Zapatero, a Socialist, was to lend his support to Schröder in the city of Dortmund on Friday. Both men were to make speeches.

Soaring unemployment

Unemployment has soared to around five million nationally and nowhere has it bit harder than in North Rhine-Westphalia, which contains the coal mines and steelworks of the Ruhr Valley.

Thirty years ago, coal and steel accounted for 830,000 jobs, now the figure is just 130,000 and as a result, unemployment in some areas tops 12 percent.

A total of 1.1 million people are unemployed across the region and the current state premier, the SPD's Peer Steinbrück of the SPD, is forced to admit on his campaign poster that he "cannot promise jobs."