Why riot in Germany when the Election comes?

300 people block crossing - injured and arrested
Injured police, demolished showcase: Bremen experienced the night before the election Sunday a violent outbreak of violence. About 300 people blocked a crossroads, laid fires and threw bottles. Bremen has come to violent riots on the night of Sunday. About 300 people blocked an intersection and threw bottles at police officers. Some officials were injured, the police said. Rioters laid fires and threw stones in shop windows.
In the state of Bremen, 478,000 eligible voters are called on Sunday to determine the government's course for the next four years. The Bremen citizenship, the state parliament of the city state, is newly elected. The ruling over 70 years SPD and the opposition CDU donated nothing in the past election campaign. The top topics were education, transport and housing policy. Both parties are close together in polls. However, the SPD must expect heavy losses.