BERLIN (Reuters) - Angela Merkel's conservatives have opened a 20-point poll lead over Germany's opposition Social Democrats (SPD), leaving the chancellor's gaffe-prone rival with even more ground to make up before September's national election.
A survey published by the Forsa institute on Wednesday put the SPD down two percentages points at 23 percent, their lowest level in 18 months and equal to their showing at the 2009 election, which was their worst since World War Two.
Merkel's conservative CDU/CSU bloc rose one point to 43 percent, its highest level since she became chancellor in 2005.
Since October, just after the SPD announced former finance minister Peer Steinbrueck would stand against the perennially popular Merkel in the autumn, the SPD has dropped seven points.
The SPD had hoped to snatch the region of Lower Saxony from the conservatives in an election taking place on Sunday, giving the centre-left much-needed momentum at the start of the federal election year.
But polls there show the large lead once held by the coalition the SPD would like to operate with the Greens has all but disappeared. They are running virtually neck-and-neck with the CDU/Free Democrat alliance - and most commentators blame Steinbrueck.
Back in October, the charismatic but unpredictable Steinbrueck was one of Germany's most popular politicians, but he has since alienated much of the voter base of a party that still vaunts its working class roots.
He revealed he earned 1.25 million euros in speeches in the last three years, said chancellors should earn more, and admitted he would never drink a bottle of wine that cost less than 5 euros.
He has also acknowledged he has a problem with female voters - something he did not help remedy by saying he thought Merkel got an unfair "bonus" in popularity terms for being a women.
The Forsa survey showed that while 59 percent of voters would back Merkel for chancellor if they could vote directly, only 18 percent favored Steinbrueck.
"(Potential SPD voters) are keeping their heads down and don't want to come out and show support for their party," Forsa chief Manfred Guellner told Stern magazine, for which the poll was conducted.
Steinbrueck's spokesman declined to comment on the poll.
Forsa put the Free Democrats - also Merkel's coalition partners at national level - up one point at 3 percent, leaving them still below the 5 percent threshold for entering parliament. The Greens got 14 percent and the Left 8 percent.
(Reporting by Madeline Chambers; Editing by Stephen Brown, John Stonestreet)