A North Carolina state senate district recently sprouted a mysterious new appendage that just happens to encompass a lawmaker's second home. The extension, and the bipartisan approval it won in the GOP-led state legislature, is a classic example of the backroom dealing that happens when lawmakers are allowed to draw their own legislative boundaries.

A little background: North Carolina Republicans redrew all of the state's legislative maps in 2011, following the 2010 Census. Democrats immediately cried foul, contending that the maps were drawn with the express purpose of solidifying Republicans' hold on power in the state.

Technically speaking, the term for this is gerrymandering — deliberately drawing legislative districts in a way that benefits your party (if you need a brief visual primer on how it works, read this). In North Carolina, the specific issue is racial gerrymandering, as Democrats have alleged Republicans intentionally diluted the political clout of black voters when they drew the maps.

Courts, by and large, have agreed. Earlier this year, a panel of federal judges tossed out the 2011 maps and told the legislature to draw new ones by Sept. 1. Lawmakers recently wrapped up their new district plans and are submitting them to the judges for approval. Critics say the new plans are just as racially gerrymandered, in their own way, as the old maps.

But allowing legislatures to draw their own boundaries invites and encourages self-interested behavior among legislators: Republicans and Democrats get together to divvy up a state's voters with a primary aim of protecting incumbents across the board

The North Carolina district with the brand new appendage vividly illustrates the point. At issue is the border, in the Fayetteville area, between Senate District 21, held by Democrat Ben Clark, and Senate District 19, home to Republican Wesley Meredith. The old map, drawn in 2011, was a sprawling, aggressively gerrymandered beast, with multiple tentacles extending from Hoke County into neighboring Fayetteville.

After courts ordered the districts to be redrawn, Clark initially supported a Democratic plan that would have drawn a fairly straightforward line between the two districts. But the Republican supermajority on the committee voted down that plan in favor of their own map with a more convoluted border.

As he explained in a Facebook post, Clark objected to the Republicans' map because it “strips Ft. Bragg and Spring Lake from our district and moves them to 19.” But there was another problem with it, too: Clark had recently built a second home in the area, according to the Fayetteville Observer. That home lay in District 19 of the Republicans' map, not Clark's own District 21.

If Clark ever wanted to make his new home his primary residence, he'd have to run against Republican incumbent Wesley Meredith in District 19. So Clark proposed adding an appendage to the new district border that would reach out and encompass his new home. Below, the Republicans' map is on the left and Clark's proposed map is on the right. The locations of Clark's homes are also indicated.

The Republican-led committee approved Clark's new plan unanimously.

“The Senate Redistricting Committee adopted criteria that included avoiding pairing incumbent legislators when drawing new legislative districts if possible,” said Committee Chairman Ralph Hise in an email. “When the first draft of the Senate map was released, Sen. Clark’s new address was not known. Sen. Clark offered an amendment to include his home in his district and the amendment passed in a unanimous bipartisan vote.”

Reached via email, Clark said that “over the course of the legislative process, parties with supermajorities tend to accept only amendments that they perceive benefit their interests.” He added he would have preferred the map submitted by Democrats, which also did not include his second home within its boundaries.

Good governance advocates argue lawmakers should not be able to draw their own legislative districts.

“I wish I were surprised” by the Clark extension, said Justin Levitt, a redistricting expert at Loyola Law School. He said that lawmakers drawing district boundaries to include home purchases is “not super-common ... but it's also not super-unusual.” Usually, Levitt said, parties in power will try to exclude opposing lawmakers' homes from certain districts to kick them out of office.

Sometimes, incumbents drawing districts will even try to exclude the homes of primary challengers. In 2002, Illinois Democratic congressman Bobby Rush redrew the borders of his district to exclude the home of then-state Sen. Barack Obama, who had challenged him in a primary several years before. But Obama, by that point, was already busy redrawing his own state senate district to set him up better for a U.S. senate run in 2004.

“The system of redistricting in the U.S. tends to allow representatives to choose people instead of people choosing representatives,” Obama said in an interview with the Hyde Park Herald in 2001. That appears to be exactly what's going on in North Carolina.

But lawmakers there fiercely oppose any attempts to take redistricting power out of their hands. At a redistricting committee meeting earlier this month, Hise dismissed the idea of a nonpartisan redistricting commission as “mythical.”

Commissions are in charge of the redistricting process in Washington, Idaho, Arizona and California.