Newly drawn election maps helped North Carolina Republicans build their majorities in both the state House and Senate Tuesday, despite the fact that their winning margins in the statewide popular vote dropped from 2010 to 2012.

The new maps made the clearest impact in the House, where election-night returns show the GOP winning 77 of 120 seats, or 64 percent of total House representation. That’s a gain of nine seats from the 2010 election.

House Republicans won those 77 seats with just short of 2 million of the 3.9 million votes cast statewide in House races, 51.1 percent of the total vote. Democrats captured 48.2 percent of the statewide popular House vote this year, while Libertarians and unaffiliated or write-in candidates won the rest.

In 2010, Republicans won control of the House for the first time since 1998 by capturing 68 seats. In contrast to Tuesday’s election, the GOP’s statewide popular vote percentage in 2010 — 58.7 percent — topped the percentage of seats won in the House chamber, 57 percent.

Republicans also picked up one seat in the state Senate in Tuesday’s election, winning 32 of 50 races. Senate Republicans matched their House counterparts by winning control of 64 percent of representation in their chamber. More than 2 million North Carolinians voted for GOP Senate candidates. They won 52.5 percent of the statewide popular vote, while Democrats won 47.1 percent.

Like their House counterparts, Senate Republicans saw their caucus grow despite a drop in statewide popular vote percentage. In 2010, Republicans won 31 Senate seats, 62 percent of the total, with 58.9 percent of the popular vote.

New election maps account for at least some of the GOP success. By winning the 2010 elections, Republicans in both the House and Senate won control of the redistricting process that generated the new maps.

Democrats and their ideological allies have challenged the maps in state court. That legal challenge continues, though judges declined to allow lawsuits to prevent use of the new maps for the 2012 election cycle.

While Democrats have cried foul over the way Republicans drafted election maps last year, a comparison of statewide popular vote margins to the percentage of representation in the House and Senate shows that recent maps drawn by Democrats also have had an impact on representation.

In 1996, Republicans won roughly 51 of the statewide votes in House races and roughly 51 percent of House seats. By contrast, 49 percent of the statewide vote in Senate races translated into only 40 percent of Senate seats for the GOP.

The gap grew larger after the 1998 election. Republicans won about 50 percent of the votes in both House and Senate races. They won 44 percent of House seats and just 30 percent of Senate seats.

In 2000, Republican candidates won 49 percent of Senate votes and just 30 percent of Senate seats. They captured a majority of statewide House votes (50.7 percent, compared to Democrats’ 47.8 percent), but won just 48 percent of House seats. That deficit translated into the Democrats holding a 62-58 House majority despite having won less than half of the statewide votes in elections to the chamber.

Democrats redrew election maps after the 2000 census. Despite a series of court rulings that generally favored Republican challenges to the Democrat-drawn maps, the next three election cycles produced results in which Republicans won a majority of the statewide popular vote for at least one of the two legislative chambers but never won control of either the House or Senate.

In 2002, House Republicans won 52 percent of the popular vote and appeared to win roughly 51 percent of the House seats. After that election, Republican Rep. Michael Decker switched parties, spurred by an illegal deal with Democratic House Speaker Jim Black, and the chamber operated for two years with an even split of 60 Democrats and 60 Republicans.

Meanwhile, Republican Senate candidates won 51 percent of the votes in the 2002 elections and picked up just 44 percent of the seats.

In 2004, after another round of court-ordered redistricting, House Republicans won 51 percent of the popular statewide vote and just 48 percent of House seats. Senate GOP candidates won 50.1 percent of the statewide vote and saw their Senate representation drop to 42 percent.

In 2006, House Republican candidates captured 50.5 percent of the statewide popular vote and saw their House representation drop to just 43 percent of House seats. Senate candidates lost the statewide popular vote to Democrats that year. Their 48 percent share of statewide votes translated into just 38 percent of Senate seats.

The 2008 election produced big shifts in the statewide popular vote totals toward Democrats, but that shift translated into almost no change in representation within the House and Senate. House Republican candidates won just 44 percent of the votes that year and maintained their share of 43 percent of House representation. Republican Senate candidates captured 47 percent of the statewide vote and 40 percent of Senate representation.

Wide gaps between the percentage of votes cast for a party and its representation in the House and Senate — including multiple consecutive election cycles in which the popular “winner” failed to capture enough seats to run either chamber — have prompted the John Locke Foundation and other groups interested in good government to advocate redistricting reform.

Mitch Kokai is an associate editor of Carolina Journal.