Exit polls suggest that Chancellor Angela Merkel's conservatives have suffered heavy losses in an election in Germany's most populous state.
Support for the Christian Democrats dropped from 35 percent to 26 percent in North Rhine-Westphalia.
The ARD television exit poll showed the center-left Social Democrats and Greens -- Germany's main opposition parties -- winning combined support of 51 percent.
That would be enough to give them a majority in the state legislature.
Some 13.2 million voters -- more than one-fifth of Germany's electorate -- were choosing a new regional parliament in the state.
Based on reporting by AP and AFP