Earlier this year, with the far-right populist Alternative for Germany (AfD) coming off a string of regional election triumphs, most observers expected Angela Merkel to become more conservative. Some within her own parliamentary bloc indeed demanded she do just that. But the opposite has happened. If anything, the chancellor and the CDU-CSU have maneuvered further left.

Part of the reason is the dictates of electoral numbers. The results of the September 24 national election meant that, with the extremes of the AfD and the Left party being deemed off-limits, Merkel's only viable coalitions involve either the center-left Social Democratic Party (SPD) or the left-wing environmentalist Greens. There is no non-left path to power.

But changes to political culture and Merkel's own personal inclinations have also encouraged realignment and effectively shifted the center further to the left. It was part of the accepted wisdom in Germany in the last 30 years that the conservatives' natural allies were the business-friendly Free Democratic Party (FDP), which has leaned towards the conservatives as coalition partner since the early 1980s, but had been in a coalition with the SPD before that.

But last Sunday, when the FDP walked out of coalition talks with the CDU-CSU and the Greens,  showed that this is no longer necessarily the case.

Read more: The FDP's Christian Lindner: The coalition killer

In justifying that decision, the FDP complained that the conservatives and the Greens had been too chummy during the negotiations. But the FDP's recalcitrance has driven Merkel and her party into the arms of another possible partner on the left - the Social Democrats.

Back to the future with the SPD?

Merkel spoke of another "grand coalition" between conservatives and Social Democrats as an option on the evening after the September 24 national election - only to be rebuffed by SPD chairman and defeated chancellor candidate Martin Schulz, who categorically ruled it out.

Schulz has now been forced to back off that hardline stance. Together with Merkel and the head of the CDU's Bavarian sister party, the CSU, the SPD chairman will be meeting next week with German President Frank-Walter Steinmeier. He's trying to broker a new government and head off a snap election. Although wary, the SPD is clearly open again to testing the Merkel option.

"We continue to regard the Grand Coalition a difficult constellation," said SPD Vice Chancellor Malu Dreyer on Friday in Berlin. "But the SPD won't refuse to engage in talks. All options have to be explored, including those between a Grand Coalition and a snap election. We'll be discussing them."

A continuation of the grand coalition would suit Merkel just fine – after all she's led two such alliances in the past 12 years. Conservatives and Social Democrats are united by pragmatism, moderation and their mutual desire for stability.

"I think the president's appeal that parties must do their best to ensure a stable government has had an effect," said the conservative state premier of North Rhine-Westphalia, Armin Laschet. "I think we should talk to the Social Democrats and pave the way for good results.

But talking to the SPD isn't the only route to a satisfactory result for Merkel's conservatives.

Breaking down the traditional political camps

Although they ultimately went up in smoke, the CDU-CSU's talks toward forming a coalition with the FDP and Greens did succeed in bringing the conservatives and the environmentalists closer together. It's the latest chapter in a trend that began with two sides working together in a handful of regional parliaments.

"There is a strong cooperation with the CDU in the regional states," former Green Member of Parliament Bärbel Höhn told DW. "Possibilities for working with the CDU have been developing in recent years. But there are still big differences between the two parties."

The warming of relations between the two parties has led to speculation about a three-way coalition between conservatives, Social Democrats and Greens or a conservative-Green minority government. They're hardly the most likely scenarios, but they do have their advocates, particularly in those parts of Germany where conservatives and Greens govern together.

"I think a conservative-Green minority government is not only imaginable but preferable," Oscar Gabriel, a former professor of political science at the University of Stuttgart, told DW. "There is sufficient common ground for conservatives to work together in a government, be it a majority or minority one…Cooperation between the two parties would encourage people not to think in terms of political camps."

That raises the question: to what extent have the traditional political camps already begun to dissolve?

The end of a traditional affinity with the FDP

The conservatives and the FDP have spent a fair chunk of postwar German history, 32 years in all, governing together nationally. But relations have deteriorated dramatically – in part because of the Free Democrats' perception that they have become Merkel's second- or even third-choice partners. The FDP accuses the Greens of coming between them and the CDU-CSU in the abortive recent coalition talks. 

"On the final evening, Ms. Merkel unfortunately decided to dissolve a compromise reached by conservatives and the FDP as a concession to the Greens," FDP chairman Christian Lindner complained to the Frankfurter Allgemeine Zeitung newspaper. "That was symptomatic for the talks." 

Both Greens and conservatives reject that notion and blame Lindner and his party for their failure to reach a preliminary coalition agreement. The Free Democrats have traditionally been described as a more centrist party, but currently, on issues such as refugees and migrants, the FDP is actually to the right of Merkel's CDU.

Lindner added that his party and the conservatives would have "doubtlessly" formed a coalition, had they possessed a majority without the Greens, and others see greater ideological affinities between the CDU-CSU and the FDP than between the conservatives and the Greens.

"We saw in the negotiations that the FDP was actually much closer to the CDU-CSU than the Greens were, so it was difficult to understand why the FDP quit the exploratory talks," Höhn said.

That may be the case, but the positive feelings to emerge from those four weeks of talking were clearly between the conservatives and the Greens.

"An important result of the long negotiations was obviously the creation of a basis of trust between some, if by no means all of the conservative and Green politicians," Gabriel said.

By contrast, after last weekend's drama, there is little trust any more between conservatives and the party that has always been their closest ally.