DRESDEN (Reuters) - Germany's Left party set an election platform attacking capitalism head on this weekend, avowing old school socialism and making any later coalition pact with the mainstream opposition seem all but impossible.
If the Left party and the center-left opposition Social Democrats (SPD) and Greens joined forces they could match Merkel's center-right government in strength, possibly even ousting the chancellor after the September 22 vote.
Yet the SPD rejects such a "red-red-green" coalition, and the uncompromising agenda of the Left party, while not ruling collaboration out, appeared to effectively end any prospect of working with a party it sees as almost indistinguishable from Merkel's conservatives.
"Time and time again I'm asked about a possible coalition with the SPD and the Greens ... but the question is, when will the SPD and Greens be ready to exit their political consensus mishmash and adhere to the will of the majority?" Left parliamentary leader Gregor Gysi told the congress.
The Left party stands at around 6-9 percent in the polls, down from 12 percent in 2009's federal election after it was weakened by internal splits. It also failed to capitalize on a financial crisis whose hardships Germany largely avoided.
Nonetheless, undiluted socialist messages rained down from the podium in Dresden over the weekend - tax the rich, nationalize the banks, redistribute wealth - all music to the ears of the 500 delegates, addressed throughout as "comrades".
Socialist books stalls, a "Solidarity with Cuba" stand and Karl Marx figurines further underscored the ideological divide.
"Let's fight for a strong Left that changes Germany and Europe," Gysi said.
He then made a series of demands of the SPD and Greens, ranging from reinstating a lower retirement age to apologizing for their sweeping welfare reforms when in power.
Bernd Riexinger, a Left leader, said the SPD and Greens set "capitalist predators into the wild" with those reforms.
"We are definitely not looking to wage an election fight as a coalition. We are fighting for our own ideas," he said.
The SPD's election campaign appears in disarray, meanwhile, with its challenger to Merkel, Peer Steinbrueck, rebuking the party's chairman Sigmar Gabriel for disloyalty.
The Left party was formed in 2007 when a group of SPD defectors based in western Germany and led by Oskar Lafontaine merged with the Party of Democratic Socialism (PDS), which grew out of East Germany's ruling communist party.
At first, the new party took German politics by storm, appealing to those who felt betrayed by the SPD's decision to create a coalition government with Merkel between 2005 and 2009.
Yet the party appeared increasingly split between a strict ideological wing of former West Germans, and a more pragmatic wing of former East Germans striving for a broader appeal.
"The Left party has lost out because the big parties are trying to present themselves as more social again, seizing on themes like a minimum wage and affordable rents," said Martin Kroh, from Germany's Institute for Economic Research.
The sidelining of Lafontaine, traditionally the harshest critic of the SPD, might help heal rifts, he said, but it was hard to see how the SPD might contemplate working with the Left.
Among the casually dressed delegates in Dresden - most either in their 20s or in their 60s - there appeared almost a preference to remain in opposition.
"We can be very effective at the town and city level, particularly in the former East, but I don't think we should abandon principles to join the SPD," said Peter Kaetzel, a retired teacher from Dresden.
(Additional reporting by Hans-Edzard Busemann and Reuters television; Editing by Alison Williams)