To quieten the dissent, Merkel has named a sometimes outspoken critic, Jens Spahn, 37, as her new health minister and recently tapped a potential successor, new CDU general secretary Annegret Kramp-Karrenbauer. But after those talks collapsed spectacularly, both the conservatives and the SPD came under pressure to revive the grand coalition, which has governed Germany for the majority of Merkel's time in office.
If she sees out a full term, Ms Merkel will have spent 16 years in office, equalling the record set by Helmut Kohl between 1982 and 1998.
Merkel is billed to first travel to the Berlin residence of German president, Frank-Walter Steinmeier, to be officially nominated.
With the initiative of Horst Seehofer, the new interior minister, a masterplan will be drawn up for more rapid processing of applications for asylum and more effective deportations.
Germany's new chief diplomat is a newcomer to foreign policy, but as justice minister was a high-profile figure in Merkel's outgoing government.
Merkel will head a coalition of her conservatives and the Social Democrats (SPD). The Social Democrats initially planned to go into opposition.
She will have to hold together what is potentially her most fragile coalition yet in what is widely expected to be her last term, while also addressing challenges such as a potential Europe-U.S. trade war and seeking agreement with France and others on the future of a fractious European Union.
An often-awkward ally to Merkel, the leader of Bavaria's Christian Social Union party becomes Germany's top security official.
But her authority was dented by her decision in 2015 to commit Germany to an open-door policy on migration, resulting in an influx of more than one million people.