Party leader Stefan Löfven and party secretary Carin Jämtin took to the op-ed pages of the daily Dagens Nyheter (DN) to announce their openness to new political constellations.
While the Social Democrats said that the Green Party was still their natural ally, "we also have things in common with the Left Party, the Liberals (Folkpartiet) and the Centre Party, and we know they can step up when needed."
The Liberals were less than seduced by the audacious flirt.
"Embarrassing," said party leader Jan Björklund, who added that the question about with whom the Social Democrats would govern if they secured an election win in 2014 was still open. "This is a non-answer. Is this the best they could come up with after pondering for a year?"
Löfven, meanwhile, dangled the bait of minister portfolios for any would-be partners and said the prime minister was "irresponsible" in his dogged determination to keep his four-party coalition intact.
"He has one solution only, regardless of how the voters vote," Löfven told the TT news agency. The op-ed also noted that both the Centre Party and the Christian Democrats were splashing about under the four-percent barrier needed to stay in parliament, meaning the government coalition might disintegrate. Thus the open invitation, but Löfven said he would try to govern Sweden without the help from the right even if the Social Democrats and the Greens ended up with more votes than the conservative Alliance, but still under the 50 percent needed for a majority government.
Left Party leader Jonas Sjöstedt, however, joined the chorus of critics but from the leftwing,
"We won't vote for a government that won't have Left Party politicians as ministers," he told TT. "If it ends up being a conservative government pushing conservative policies, they cannot count on our support."
Sjöstedt was quick to add that he preferred Löfven to the current prime minister, Fredrik Reinfeldt.
Neither the Centre Party leader Annie Lööf nor any spokesperson for the Centre Party were available to comment on the cross-bloc invite. Neither did the Christian Democrats immediately offer a reaction.
Jimmie Åkesson, leader of the Sweden Democrats, took to Twitter to comment on Löfven and Jämtin ruling out any collaboration with his minority party, which is critical of immigration and largely considered populist and xenophobic.
"Löfven's answer is basically not an answer. It's almost a parody," Åkesson tweeted.
The developments come on the same day as a new poll was published showing the Sweden Democrats have support of 11.9 percent of the the voters, making them Sweden's third-largest party, just ahead of the Greens, which polled at 11.8 percent.
The Sweden Democrat tally was two points higher than last month's Demoskop poll, which was published in the Expressen newspaper, but isn't statistically significant.
The poll also showed declines for the Social Democrats (-2.1 percent, 31.1 percent) and the Moderates (-1.0 percent to 25.6 percent).