BERLIN — The leaders of Germany’s main establishment political parties emerged from overnight talks Friday morning with the outline of a possible coalition deal, bringing Europe’s biggest economy one step closer to forming another government led by Chancellor Angela Merkel.

But many obstacles remain, not least a vote by members of one of the three parties, many of whom are less than thrilled to see the potential repeat of a coalition that has seen their vote share drop to postwar lows.

The marathon negotiation session, which went on for nearly 24 hours, was the final round in six days of preliminary talks among Ms. Merkel of the center-right Christian Democrats; Horst Seehofer of their conservative Bavarian sister party, the Christian Social Union; and Martin Schulz of the center-left Social Democrats — the three parties that have governed Germany together in a “grand coalition” since late 2013.

All three lost votes and seats in the Sept. 24 elections, making the Social Democrats, in particular, reluctant to resume that arrangement. But the success of the populist Alternative for Germany, which became the first far-right party to win seats in Parliament since World War II, made it impossible for Ms. Merkel to command a majority without the support either of the Social Democrats or of a disparate group of minor parties.