Germany's election: Coalition scenarios
It is pretty well certain that no party will win enough seats in the German parliament (Bundestag) to command a majority in the elections on Sunday.
Whoever forms the government will have to do so in coalition with another party. That is how it has been in every post-war parliament and nobody thinks it will be different this time.
At the moment, the government is formed of the centre-right Christian Democrats (CDU/CSU) in coalition with the smaller Free Democrats (FDP). Together, they have 332 seats compared with 290 held by the Social Democrats (SPD), the Greens and the descendants of the old communist party, Die Linke.
Four main scenarios are possible.
The current coalition may well win again - and then the government of Angela Merkel sails on as before. But the cloud on the horizon for Chancellor Merkel is the diminished popularity of the FDP since the last election in 2009. In pre-election opinion polls, it has been hovering just above 5% compared with around 15% four years ago.
If the FDP fails to get 5% of the vote, the law says it gets no seats in parliament. If it does reach 5% but still gets far fewer seats than its current 93, then it may not have enough weight to keep the current coalition in power.
Either way, the current "black-yellow" configuration of the government is threatened.
If the current coalition falls, all eyes turn to the possibility of a "red-green" coalition - the SPD/Greens. The leadership of the Greens has ruled out a coalition with the CDU but would go into government with the SPD.
It has already done so in the state of Baden-Wuerttemberg. It may happen at the national level after 22 September though the pre-election opinion polls indicated that the numbers were not there for this coalition, either.
Might Die Linke help? This is the party descended from the communists, though it has eschewed hard-left politics and offers itself as a left-wing democratic party (its posters emphasise that it does not want a revolution).
The problem there is that the centre-left SPD has ruled out governing with Die Linke. That may be partly a matter of pre-election expediency - the SPD might lose more votes than it gains from promising such a post-election hook-up. In the cold light of a post-election dawn, that might change - but it is not likely.
Which brings us to the Grand Coalition (a "black-red" coalition across the divide, between the SPD and the CDU).
This combination might be inconceivable in many countries but in Germany this red-black combination was precisely the complexion of the government from 2005. Indeed, Peer Steinbrueck, the current SPD contender for chancellor, was finance minister to Chancellor Merkel in that government.
This time, Mr Steinbrueck has said he will not participate in such a Grand Coalition. However, his party has not ruled it out, so it remains a real possibility, but without him.
There is a rogue card in all this, and that is the Alternative fuer Deutschland.
The only avowedly anti-euro party has been dismissed by the mainstream German media, but there is a view that its support has been understated in the opinion polls, and it could get at least 5% of the vote, and so seats in parliament. This would be a real shaking of the political ground.
If it did win seats, its likely ally would be the CDU (from which many of its members come) but they would be uneasy companions, with Alternative proving much tougher on euro bailouts, for example.
They have a fundamental disagreement on a central part of foreign and economic policy: Alternative wants the euro dead while the CDU is wedded to it.
But if Alternative won enough seats, for the first time, an out-and-out sceptical voice would get a big platform - and a vote - in debates on Europe.