The trick to gerrymandering a purple state isn't to give your party huge, unassailable margins in already friendly terrain; that's actually counterproductive. Rather, the goal is to cram your opponents into a handful of districts, then give yourself smaller margins in more districts, thus enabling you to maximize your representation in Congress or the legislature.
That's how you get a situation in which a Republican president narrowly wins North Carolina and a Republican governor loses by a smidgen, but the Republicans win supermajorities in both chambers of the legislature and have 10–3 dominance in the state's congressional delegation.
The maps that helped decide the current General Assembly were, of course, found to be unconstitutional racial gerrymanders by the U.S. Supreme Court. This week, the legislature is approving new maps—drawn by the same GOP consultant who crafted the racial gerrymanders in 2011—ahead of a September 1 deadline from a federal court. And while lawmakers say they've taken race completely out of the equation, the new districts nonetheless seem to ensure Republican supermajorities, albeit perhaps slightly smaller ones than the existing supermajorities.
Take the state Senate, where Republicans control thirty-five of fifty seats. Using the presidential vote as a proxy—since split tickets are largely a remnant of a bygone, less partisan era, this is the best indication of how a district will vote in most cases—we see that, under the districts the Senate preliminarily approved Monday, Democrat Hillary Clinton would have prevailed in seventeen districts to Republican Donald Trump's thirty-three, though Trump won the state by less than four percentage points.
What's more striking, though, is that only a scant handful of districts can be deemed even remotely competitive. Only five districts were won by less than five percentage points; of those, only one went for Clinton. So even if Clinton tied Trump in North Carolina, and her extra vote was evenly distributed throughout the state, the Democrats would have netted nothing. Meanwhile, the Dems have several districts that went for Clinton by 66, 59, 56, 55, and 48 points, all larger than Trump's friendliest district.
That's how you lock in a home-court advantage.