Germany's coalitions: What happens next? For example, the rules mean that if a party does much better in the first vote than they do in the second, all the other parties get compensated, so that the overall tally of seats matches the second vote. This can be achieved by increasing the number of MPs overall as was the case at the last election, when an additional 22 seats were allocated, taking the total to 620. German voters sometimes split their choices at the ballot - voting for a Christian Democrat MP but then tactically giving their second vote to the CDU's coalition partners, the Free Democrats, for example. In the last election, Angela Merkel's party won 237 seats and was able to secure a majority with the Free Democrats (FDP) 93 seats. In Germany's colour-coded political language, this is described as 'black-yellow' - black is the colour of Angela Merkel's party, the CDU, and yellow for the FDP. Based on the polls, there are two likely scenarios - and two unlikely ones. Most likely coalitions Business as usual: LIKELY Black-yellow. The polls show the CDU averaging 39 per cent and their current partners the FDP on 6 per cent, falling short of a majority. If the Eurosceptic Alternative für Deutschland does well, it is likely to squeeze these two main centre-right parties. The FDP could even fall below 5 per cent, eliminating them from the Bundestag altogether. The FDP has begged Angela Merkel supporters for their backing in the 'second vote', but Mrs Merkel insists her party is fighting for every ballot. However, on key questions like tax and Europe, the FDP remains the most like-minded partner for the CDU. Both parties oppose tax rises and mutualisation of debt across European states. A grand coalition: LIKELY Black-red. The Social Democrats (SPD), the main opposition party, average around 26 per cent in the polls. Their allies the Greens have slumped to around 9 per cent. The SPD has called a meeting of its leadership for September 27, five days after the election, that is expected to discuss the prospect of a grand coalition with the CDU. Mrs Merkel led a grand coalition between 2005 and 2009. The SPD's current leader, Peer Steinbrück, was her finance minister. That ended badly for the SPD; their 23 per cent result in the 2009 elections was their worst since the Second World War. The CDU and SPD have contrasting views on tax, Europe and the minimum wage. The SPD wants to increase the top rate of income tax, introduce a national minimum wage, and has proposed setting up a debt redemption fund, which would guarantee European debt jointly A left wing coalition: UNLIKELY Red-Green-Red. This would be a government of the SPD and the Greens propped up by Die Linke, the far-left party descended from the Communist rulers of East Germany. The SPD has however, already ruled this out - and given die Linke's roots, any cooperation with them would be regarded with hostility by voters with memories of the Wall and the Stasi. Both the CDU and FDP have used this unlikely scenario as a tactic with which to scare undecided voters during the campaign. The outside bet: UNLIKELY Black-Green. A coalition with the Greens would secure a majority for Angela Merkel's party. But given how apart the two parties are on policy areas like tax and Europe, it would be an unlikely and unstable alliance.