Tuesday's news that South Carolina will get another congressional seat predictably prompted speculation about how redistricting will affect voting outcomes in our state. But no speculation is needed to explain why the extra seat was created: It's because plenty of Americans have voted with their feet over the last quarter century by moving here.

According to 2010 U.S. Census statistics released Tuesday, over the past decade, South Carolina's population rose by 15.3 percent to 4.6 million -- an even higher rate than the South overall (14.3 percent). That's proof positive that despite growing pains, the Palmetto State is an inviting place to live.

Of course, those many newcomers bring not just new opportunities but new challenges. We must balance that population -- and economic -- growth with measures to preserve the quality of life that attracts so many people to join us. That includes protecting our state's invaluable natural heritage, from the coastal beaches and wetlands to the mountains of its northwest corner.

But protecting partisan turf should not be the driving force for the Republican-controlled General Assembly and Republican Gov.-elect Nikki Haley as they ponder how to re-slice our state's political pie into seven congressional districts.

Sure, to election victors have long gone the gerrymandering spoils of drawing districts in a manner that favors them. But a troubling recent U.S. trend has taken that tradition to ridiculous lengths, producing convoluted districts that are "safe" for one party or another due to computer-aided concentration of either likely Republican or Democratic voters. Such districts are drawn with no regard for municipal and natural boundaries -- only with the overriding goal of safeguarding one party or the other.

Such warped shapes minimize general-election competition, with U.S. House members often facing a greater risk from within their parties than the other party. For instance, 14-term 5th District Democratic incumbent John Spratt's loss to GOP challenger Mick Mulvaney in November marked the first party change in an S.C. congressional seat since 1994, eight election cycles ago, when Republican Lindsey Graham won the 3rd District after Democratic incumbent Butler Derrick stepped down.

South Carolina does have four new federal lawmakers, all Republicans, entering the U.S. House next month -- Mr. Mulvaney, Tim Scott (1st District), Jeff Duncan (3rd) and Trey Gowdy (4th). But Mr. Scott and Mr. Duncan are replacing, respectively, GOP incumbents Henry Brown and Gresham Barrett, both of whom didn't seek re-election. And Mr. Gowdy ousted GOP incumbent Bob Inglis in June's primary.

Unfortunately and inevitably, inter-party competition generally forces Republicans to the right, Democrats to the left and chances of bipartisan cooperation to long-shot status.

Our state lawmakers and governor should re-draw congressional districts in a fair, balanced and geographically cohesive manner. That won't just make our district shapes far less contorted. It will make our state's U.S. House general-election races more competitive -- and its winners more accountable to a wider range of voters.