All the states experiencing a switch in legislative control held elections under districts drawn by a court or another body outside the state legislature.
North Carolina's courts got involved in the state's redistricting when Republican legislators filed a lawsuit claiming that redistricting maps, drawn primarily by the General Assembly's Democratic majority, gave Democrats an unfair advantage and violated the state's constitution.
Ultimately, the N.C. Superior Court ruled that the General Assembly could not resolve the problem internally and Judge Knox Jenkins redrew the district lines. The N.C. Supreme Court upheld the actions of the Superior Court.
This struggle to control district lines is not unusual, said Ken Shotts, a political science professor at Northwestern University.
The demographic and ideological breakup of a district can determine a legislator's political future, he said. Legislators quickly object if redistricting could hurt them or their party.
"Basically, for every plan that's adopted, there is going to be one or many lawsuits against it," Shotts said.
Some states -- such as Iowa -- have avoided partisan battles over redistricting by using outside, nonpartisan bodies to expedite the process.
In 1971 and 1972, Iowa's Supreme Court was forced to draw district lines because partisan disputes in the legislature made compromise impossible, said Gary Rudicil, a representative of Iowa's Legislative Service Bureau. "We used to do it like every other state -- the Senate and the House just fought it out," Rudicil said.
In the early 1980s, Iowa responded by creating the Legislative Service Bureau to collaborate with its state legislature on redistricting, Rudicil said.