According to the "Basic Law of the German Federal Republic", that is, the German Constitution, the country's legislative bodies are the Bundestag and the Bundesrat. The former is directly elected by all German voters, and the latter is elected by the German federations. The state government is composed of members who represent the will and interests of each state. In the elected federal parliament, the party with more than 50% of the seats becomes the ruling party. If a single party holds less than 50% of the seats, it can also govern in coalition with other parties, as long as the total number of seats of all parties in the alliance is More than 50% is enough. The currently ruling Christian Democratic Union (Christian Social Union) and the Social Democratic Party are a coalition government. Since the two parties are the two largest political parties in Germany, this coalition government is also called a "grand coalition government."

In the direct election of the Bundestag, Germany implements a "two-vote system": the first vote of the electorate is for the candidate running in his own name in the constituency, and the second vote is for the political party. . The first-vote counting system adopts a relative majority representation system. The elected candidate does not necessarily need to obtain more than half of the votes in the constituency. As long as he obtains the most votes among the candidates, he can be elected; the second-vote counting system adopts a proportional representation system. Each state The number of second votes obtained by each political party will be counted separately, and seats will be allocated to each political party in accordance with the proportional principles stipulated by law.

There is an important rule in the German electoral system, known as the 5% clause, that is, only parties that obtain at least 5% of the votes in the party vote (i.e. the second vote) and obtain at least 3 constituency seats Only then can you formally enter the parliament. For political parties that do not meet the conditions for seat allocation and for political parties that obtain more than three directly elected seats but do not reach 5% of the party vote, their members can only participate in parliamentary activities in their own names and cannot form parliamentary groups. This move was based on the lessons learned during the Weimar War. At that time, small parties were not restricted from entering parliament, which led to Hitler later relying on the numerical advantage of small parties to come to power and usurp power.

Germany’s two-vote system is actually an electoral system based on proportional representation and supplemented by majority representation. The calculation of votes and the number of seats for each political party must be based on the second vote. This system determines the emergence of a governing coalition in many cases, because it is basically impossible for a single party to obtain more than half of the seats in parliament under the current situation.