More than half of the states in the U.S. are at “extreme risk” of congressional districts being redrawn to unfairly favor one party, according to a study of redistricting processes by RepresentUs, an advocacy group focusing on election reform.

In South Carolina, congressional and state legislative district boundaries are drawn and approved by members of state legislature. These lines are subject to veto by the governor.

After one of the most contentious elections in modern history, redistricting is even more chaotic than usual, according to RepresentUs CEO Josh Silver.

The chaos is due in part to Supreme Court rulings since the last census that block partisan gerrymandering lawsuits from federal courts and end requirements for some states to get redrawn maps pre-cleared by the federal Justice Department.

The Palmetto State’s redistricting committees adopted guidelines in 2011 that recommend all congressional and state legislative districts be contiguous and “attempt to preserve communities of interest and cores of incumbents’ existing districts,” according to ballotpedia.org.

RepresentUs researchers asked at five key questions to determine the risk for gerrymandering:

  • Are elected officials or nonpartisan commissions are in charge of drawing maps?
  • Can map-drawing can be done in secret?
  • Does one party control the process?
  • What are state criteria around how districts must be drawn?
  • How hard it is to challenge gerrymandered maps in court?

The answers were used to narrow the study to three metrics regarding the secrecy of drawing maps, partisan gain and the difficulty of challenging rigged maps in court.

South Carolina, according to the study, is at high risk in all three metrics.

“At the end of a 10-year [redistricting] cycle, the state can look very different than it did before,” lead researcher Jack Noland, told Axios, a Virginia-based news website. “That is all the more reason that we need fairer lines from the beginning, to sort of withstand those changes.”

Only seven states received a minimal risk rating: California, Colorado, Hawaii, Michigan, Arizona, Washington and Idaho.