Complex sentence: In 2011, the Greens made large gains in Rhineland-Palatinate and in Baden-Württemberg, where they became the senior partner in a governing coalition for the first time.
Split into simpler sentences: In 2011, the Greens made large gains in Rhineland-Palatinate and in Baden-Württemberg. In Baden-Württemberg they became the senior partner in a governing coalition for the first time.