The last six months have given Republicans plenty of reasons to celebrate.

In November, a set of redistricting maps approved by the GOP-led General Assembly passed a major hurdle when the U.S. Justice Department determined that the new boundaries don’t infringe on federal civil-rights protections. It was the first time in decades that the federal government OK’d North Carolina’s redistricting plan without a hitch.

Another blow to Democrats came two months later when a state court declined to postpone the Tar Heel State’s election schedule while lawsuits against the redrawn maps proceed, meaning that districts favorable to Republicans will be used in the 2012 election.

Inciting even more glee in Republican circles, Democratic incumbents in North Carolina have been jumping ship in droves. The highest profile retirement came in late January when Gov. Bev Perdue announced that she wouldn’t stand for re-election. Neither will Democratic U.S. Reps. Heath Shuler, of the 11th Congressional District, and Brad Miller, of the 13th Congressional District.

As of mid-February, 18 Democrats in the state legislature had announced either their retirements or plans to seek another office.

Given that troubled political atmosphere, do Democrats have cause for optimism? Several political analysts say yes. The reason: The impact of a gerrymandered redistricting plan diminishes over time as political and demographic factors shift. That presents opportunities for the political party not in power — in this case, the Democrats — to make inroads.

“It’s very difficult to predict what’s going to happen” in the future, said Andrew Taylor, a political science professor at North Carolina State University. “Changes in population, people moving out of the state, people moving into the state, people moving within the state, and issues cropping up nationally and at the state level.”

For instance, Republicans made historic gains in the state legislature in 2010 under a set of district maps created by Democrats after the 2000 census. A national tide hostile to Democrats, along with favorable dynamics at the state level, swept the GOP into power, notwithstanding the Democratic gerrymander from the past decade.

“Once you get two or three cycles out from the redistricting decision, the effects wear off and it becomes much more difficult for the political parties to plan,” Taylor said.

Political analyst Michael Shear echoed that view in The New York Times in November. “Redistricting does not determine the outcome of every race,” he wrote. “Campaigns still have to be waged, and strong candidates can still defeat poor ones, even in districts with voting histories that would suggest the stronger candidate has an uphill battle.”

Republican gerrymander

That’s not to underestimate the value of the redrawn maps to the GOP’s political fortunes. District data compiled by the conservative Civitas Institute and the pro-business N.C. FreeEnterprise Foundation show that Republicans drew themselves a decided advantage in the new district boundaries.

Under the old maps in 2010, Civitas split the partisan advantage almost evenly between the parties in the state Senate — 27 seats went to Republicans and 23 seats to Democrats. But under the new plan, Republicans have a 32-to-17-seat advantage. One district ranks neutral.

On the House side, Civitas gave Republicans a 63-to-54-seat edge in 2010, with three seats neutral. In 2012, that advantage has grown to 78 seats for Republicans and 42 seats for Democrats. None are neutral.

Similarly, NCFEF’s rankings under the old plan put 24 Senate seats in either the “strong” or “lean” Democratic categories, and 21 seats in either the “strong” or “lean” Republican categories. Five seats were swing. Under the new plan, the partisan edge shifted in favor of Republicans by a 27-to-18-seat advantage. Five seats are swing.

In the House, NCFEF gave Democrats a 56-to-50-seat leg up under the old maps (14 seats were swing). That shifted to a 66-to-44-seat edge for Republicans in the new plan (10 seats are swing).

‘Dummymander’

Even with that built-in advantage, a long-term Republican majority isn’t guaranteed. Particularly in a repeat of anti-GOP election cycle like 2008, Democrats could pick up swing and Republican-leaning districts, putting a legislative majority within reach.

That raises the chief paradox of redistricting: In order to maximize the number of winnable districts, partisan map-drawers distribute favorable votes as broadly as possible in hopes of winning by a small margin in many districts and losing by a substantial margin in a few.

That strategy could backfire in a poor political year for the majority party, a development tagged by political scientists as a “dummymander.”

A prime example is North Carolina’s 13-district congressional delegation. In 2010, NCFEF identified two congressional seats as “lean” Republican and four as “strong” Republican. But under the new lines, 10 seats are “lean” Republican; none fall into the “strong” category.

“You’re planning on your people winning by a little and losing by a lot,” Taylor said. “Therefore, if you plan on winning by a little, and you get a national tide, that could be problematic.”

Two specific examples are the 3rd and 6th congressional districts. Republicans have dominated the two districts for over 15 years, but political experts say that could change in the future.

“In a good year for Democrats, where they have the wind in their sails because of some national momentum advantage, a strong Democrat could very easily defeat a mediocre or weak Republican in those two districts,” said John Davis, a Republican political consultant in Raleigh.

Retirement opportunity

Retirement is another factor that could lead to Democratic gains in the future. A reverse of that scenario cropped up in 2010, when Democrats still controlled the General Assembly. A number of key Democrats in the legislature, particularly the Senate, chose retirement rather than face a rough-and-tumble re-election campaign.

The retirement of Democrat R.C. Soles, the longest serving member of the state Senate, cleared the way for Bill Rabon to win the district for Republicans for the first time in over three decades. Even more, Rabon won by a sizable margin — 64 percent to 36 percent — over his Democratic opponent, former state House member David Redwine.

Tony Rand, another stalwart of Senate Democrats, retired in 2009. The following year, Republican Wesley Meredith snatched the seat from Rand’s appointed replacement, Margaret Dickson.

Also in 2010, Democrat David Hoyle opted to not seek a 10th term in the Senate. Republican Kathy Harrington won the seat by beating her Democratic opponent, Jim Long, 70 percent to 30 percent.

Even longtime legislators who didn’t retire in 2010 faced a brutal time at the polls. Republican challenger Rayne Brown thrashed then-House Majority Leader Hugh Holliman of Davidson County 57 percent to 43 percent. Holliman had served six terms in the House.

David N. Bass is an associate editor of Carolina Journal.