1) Black-yellow: CDU-CSU in coalition with the FDP


Merkel's preferred scenario, that would give Germany its first right-wing government in 11 years. This requires the CDU-CSU alliance to top the poll to have first crack at forming a coalition and for the CDU-CSU and the FDP between them to win more than 50% of seats in the Bundestag. Latest polls gave them 35% (CDU-CSU) and 13.5 (FDP) - a total of 48.5%.


2) Black-red, or grand, coalition between the two big parties (CDU-CSU and SPD)


This would be a continuation of the sometimes awkward centrist coalition of Merkel's first term as chancellor, and is favoured by the SPD. A grand coalition would easily have a majority - latest polls give the SPD between 24% and 27% - making a total of around 60%. Some say a new grand coalition would be unstable. But they said the same four years ago.


3) Jamaica (black, yellow, green) coalition between CDU-CSU, FDP & greens


A combination canvassed after the 2005 election and might be a last resort if the CDU-CSU and FDP do not have enough seats between them to form a majority. But they would be awkward bedfellows ? even though Merkel, a former environment minister, has a strong 'green' streak - and the Greens have said they would not be interested. The prospect of even a small share of power might change that, though.


4) Traffic lights (red, yellow, green) coalition between SPD, FDP and Greens


This, too, was a possibility in 2005 and in 2002 and would return the centre left to power. But this same combination was scuppered by the FDP which refused to join up with parties on the left. The FDP leader at both those elections is still FDP leader and insists he would make the same decision this time around. Between them, though, the SPD, at 24%, the FDP at 13, and the Greens at a projected 10%, could make it to 50%. Only possible if Merkel is unable to form a CDU-CSU led coalition


5) Red-red-green: (SPD, Linke and Greens)


Ideologically coherent and logistically possible, if these left-orientated parties do just a little better than projected. But the SPD has said it will never form a coalition with the Linke, whose roots lie in former East Germany. Some believe it would break that pledge if including the Linke made the difference between forming a government or not.


6) Red-black: Merkel's grand coalition in reverse


Perhaps the most dramatic option, if the SPD managed to overtake the CDU - which is unlikely to impossible - and so win the right to form the next government. Highly doubtful that the CDU-CSU would agree to join, and Merkel would almost certainly resign as party leader.


Excluded


A centre-right CDU-CSU government: with, at best, a projected 35% share of the vote, the CDU-CSU would be unable to govern alone. A centre-left SPD government with, at best, 27% of the vote, belongs in fantasy land.