By Noah Barkin
BERLIN, Jan 15 (Reuters) - A prominent regional politician who has been a member of Germany's Social Democrats (SPD) for more than four decades has quit the party and joined its far-left rivals in a blow for the SPD days before a state election.
Sigrid Leuschner, an SPD lawmaker in the Lower Saxony assembly for 19 years, said her decision to move to the Left Party was based on concerns that the SPD had become "devoid of substance".
She also cited disappointment with Peer Steinbrueck, the SPD candidate for chancellor, who has slid in opinion polls amid outrage over lucrative speaking engagements and a series of gaffes.
Leuschner had been forced to cede her longtime voting district to the wife of former German chancellor Gerhard Schroeder following an internal party vote last year.
The defection is an embarrassment for the SPD before an election on Sunday in Lower Saxony that is seen by many as a trial-run for the federal vote eight months later.
Until recently, the SPD and Greens had been expected to win a majority in the state vote, ousting Christian Democrat (CDU) premier David McAllister, a loyal ally of Chancellor Angela Merkel, and generating much-needed momentum.
But recent surveys suggest the contest could be extremely close, with McAllister within shot of victory if his Free Democrat (FDP) coalition allies manage to make it over the five percent threshold for entering the state assembly.
Some have blamed recent SPD weakness in the state on Steinbrueck, a 66-year-old former finance minister whose acerbic style has not gone down well with voters since he was anointed Merkel's challenger in September.
"If the SPD does lose in Lower Saxony after being ahead in the polls for the past year it will be blamed on Steinbrueck," said Peter Loesche, emeritus professor of political science at Goettingen University.
But he rejected suggestions the SPD was doomed to defeat in the federal vote if they lose on Sunday.
"A lot can happen in eight months. Much will depend on the economy. If it holds up the SPD has no chance. But if ordinary people start feeling the euro crisis then things can change."
Speaking on Monday night, Leuschner expressed disappointment over Steinbrueck's comments that he would not be inclined to drink a bottle of wine that cost less than five euros.
"You don't make fun of poor people," Leuschner said.
The SPD voted in March of last year to give Doris Schroeder-Koepf, the 49-year-old wife of the former chancellor, a shot at the regional assembly seat that Leuschner had held. The 61-year old SPD veteran said she felt stabbed in the back by her party.
Steinbrueck's wine comments and his remarks in a newspaper interview two weeks ago that German chancellors were underpaid compared to bank managers have compounded his image problem in a party that has traditionally defended the poor.
Shortly after he was named to take on Merkel, it emerged that Steinbrueck, a member of parliament, had made some 1.2 million euros over the past three years from speaking engagements.
German media have speculated he could come under pressure to bow out of the national race if the centre-left fails to win in Lower Saxony, although party chairman Sigmar Gabriel dismissed this as rubbish over the weekend.
Recent polls have shown the centre-right of CDU and FDP with close to 45 percent of the vote in Lower Saxony and the centre-left of SPD and Greens on 46 percent. (Reporting by Noah Barkin, editing by Gareth Jones and Angus MacSwan)