EXPLAINER-How will the result of the Saxony-Anhalt election be decided?

The eastern state of Saxony-Anhalt holds an election on Sunday that ​could see the far-right Alternative for Germany (AfD) party win power ​in a German state for the first time. The ‌AfD ​has been leading in polls, with surveys regularly putting support at over 40%, 10 to 15 points or more ahead of the conservative Christian Democrat party (CDU), which currently leads a ‌coalition with the centre-left Social Democrats (SPD) and the pro-free-market Free Democrats (FDP).

But whether the AfD's main candidate Ulrich Siegmund becomes state premier is likely to depend on whether enough of the other parties opposed to the far-right gain enough votes to enter parliament. Surveys indicate the FDP is ‌likely to miss out, but if both the SPD and the environmental Greens clear the minimum 5% threshold, their votes — together ‌with those of the CDU and the far-left Left Party — could keep the AfD from forming a government.

Apart from the small far-left BSW party, which polls suggest is unlikely to pass the 5% threshold, all the other parties have ruled out joining a coalition with the AfD, which has also said it aims ⁠to ​govern alone. Polls have indicated that ⁠CDU State Premier Sven Schulze is ahead of Siegmund as voters' preferred choice for state premier. But whether Schulze would be able to form a government ⁠is unclear.

Combining with the SPD and Greens may not be enough for a majority and the CDU has ruled out a coalition with the ​Left Party. It has not said how it could form a majority without their support. One possibility is a minority government ⁠led by Schulze that would depend on passive tolerance from the Left Party. In the neighbouring state of Thuringia, a CDU premier in coalition with the SPD and ⁠the ​BSW depends on cooperation from the opposition Left Party to pass legislation.

One area of uncertainty is the number of seats in the state parliament or Landtag, which has a minimum of 83 seats but which can have more depending on the ⁠breakdown of the vote. Currently there are 97 members of state parliament. That is due to the mix of constituency seats won ⁠directly in single-member districts and seats ⁠allocated proportionately based on party-list votes.

If a party wins more of the 41 constituency seats than would be proportionate to its overall share of the vote, it keeps those seats as so-called overhang ‌mandates, with extra ‌balancing mandates awarded to the other parties to ensure proportionality.