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An electoral tidal wave propelled Republicans to a majority in the House of Representatives in 2010.

But an electoral tidal wave at the state and local level in 2010 may be what helps the GOP maintain that House majority in 2012.

This is the first election year following 2010's decennial census. The census documents the nation's population and demographic shifts. As a result, the census dictates a re-allocation of Congressional seats. For instance, Texas gained a whopping four seats. Ohio lost two. California remained the same. The census also allows states to redraw the lines of Congressional districts to better fit their evolving populations - or for political gain.

Most states spent the past two years jiggering the lines of their Congressional districts. 2010 became a celebrated year for Republicans. Voters awarded the GOP a net pickup of 63 seats in the House. That gave Republicans their highest number of House seats since 1938.

But the great untold story of 2010 is not what the GOP did in House contests. It's how they performed down the ballot.

"Democrats couldn't have picked a worse year to have a terrible election cycle than 2010," said David Wasserman who handicaps House contests for the non-partisan Cook Political Report. "Because Republicans, through one election, got the opportunity to redraw the map for the next ten years."

In other words, the GOP made extraordinary gains in the House in 2010. And via redistricting in 2012, Republicans were able to design their own battlefield that played to their strengths.

Forty-four state legislatures control the process which governs mapping of Congressional districts. While the GOP was busy capturing seats hand over fist for House contests, they simultaneously flipped the majority in 19 Democratic state legislatures, wining close to 700 seats. It marked the first time Republicans had been in charge of so many state legislatures since the late 1920s. Republicans even seized the state Senate in Minnesota, something that had never happened before. The GOP won 11 governorships from Democrats, too.

"In my estimation, Republicans didn't really claim an extra advantage in the House through redistricting. But they saved about a dozen seats that they would have otherwise lost in 2012 if they hadn't undergone the remap," said Wasserman. "What they were able to do was take a lot of the 87 freshmen who won seats - a lot of whom unseated Democrats in 2010 and removed Democratic voters from their districts so they would have an easier time winning re-election."

In their book "It's Even Worse Than It Looks," political scientists Tom Mann of the Brookings Institution and Norm Ornstein of the American Enterprise Institute explained the impact of the GOP's down-the-ballot successes in 2010 like this:

"Redistricting has become a major front in the permanent campaign of both parties. The parties devote enormous energy and resources to winning control of key state legislatures and governorships and then designing, enticing, and defending in the court the maps that advance the interests of the controlling party. Party members in Congress and state legislatures find their own interests in reelection and majority status importantly connected to these efforts, which makes them even more inclined to cooperate with the strategic partisan team play that drains the policy-making process of its deliberative capacity," they wrote.

A perfect example of this unfolded in 2010 when Rep. Blake Farenthold (R-TX) unexpectedly toppled Rep. Solomon Ortiz (D-TX) by a mere 799 votes.

Freshmen lawmakers who upset longtime incumbents in wave elections by such a thin margin are often dead ducks the next time around. But as mentioned earlier, Texas gained four Congressional seats after the census. By redrawing the lines for 2012, Republicans who control the redistricting process in Texas were able to inoculate Farenthold, making his district significantly more Republican this round. Had Farenthold run in any other year, he would have stood for re-election in a district that sent the same Democrat to Congress with little opposition for 15 consecutive elections.

David Wasserman says that Farenthold would have been a "total, hopeless case for reelection" without redistricting. But because of redistricting, "there are a lot of other Blake Farentholds out there on the Republican side."

This is the "Harold and the Purple Crayon" phenomenon of politics. Many will remember a grade school book about four-year-old Harold who wields a powerful purple crayon. Harold deploys the purple crayon to draw whatever he needs. He draws a moon on a moonless night. He fashions a sidewalk when he wants to take a stroll. He draws pies when he's hungry and a sailboat to escape from a dragon.

Success in state government elections bestowed Republicans with a powerful, purple crayon. The GOP didn't draw pies or boats. But they did draw their own political reality for redistricting.

This created a beast of a task for Democrats when it comes to winning back control of the House.

"It's going to take a Democratic wave of the likes we saw in 2006 or 2008 in order to get Democrats anywhere near the majority in the House," Wasserman said.

By the same token, Democrats had a purple crayon of their own in Illinois where Democrats control the redistricting process. Democrats have created tough re-elections for Reps. Bob Dold (R-IL), Judy Biggert (R-IL), Bobby Schilling (R-IL) and others in the Land of Lincoln. Democrats are also banking on picking up seats in California where a non-partisan redistricting commission drew multiple sitting lawmakers - Democrats and Republicans alike - into the same districts. Prior to this cycle, California held the dubious distinction of rarely having a competitive House race. That's changed for this round.

What's interesting is that most analysts and even political partisans regard redistricting to essentially be a wash for the parties - when it comes to which side came out ahead.

"Due to the nature of redistricting, we have opportunities that Democrats are poised to pick up," said Jesse Ferguson of the Democratic Congressional Campaign Committee (DCCC), the national organization devoted to electing House Democrats. "Are there as many opportunities for Democrats? Absolutely."

Ferguson's counterpart is Paul Lindsay at the National Republican Congressional Committee (NRCC), which commits itself to electing House GOPers.

"There wasn't a party that gained a huge advantage over the other," says Lindsay.

But the main issue is that Republicans won in states where they could potentially shield most vulnerable candidates.

"If you had to pick a state that six or seven beer goggles ugly for Democrats in redistricting it was North Carolina," said David Wasserman. "Republicans - once they took control this cycle (of redistricting) were able to un-gerrymander the districts and gerrymander them in favor of Republicans and pick up as many as four seats."

Democrats currently hold a 7-6 advantage among the Tar Heel State's 13 Congressional districts. But Republicans have a chance to switch that to as high as 10-3 in their favor.

Freshman Rep. Renee Ellmers (R-NC) defeated Rep. Bob Etheridge (D-NC) by just under 1,500 votes in 2010. Typically, Ellmers would be ripe for the picking in the next contest. But redistricting helped her a lot in 2012. Now the GOP is making serious runs at Reps. Larry Kissell (D-NC) and Mike McIntyre (D-NC). And conservative Blue Dog Rep. Heath Shuler (D-NC) elected to retire.

Conventional math reveals that Democrats need to win 25-plus seats to re-take the House. But the true figure is higher than that. Redistricting made it easier for Republicans to protect many of their incumbents. Otherwise, Democrats would stand a better chance of winning the House in 2012.

This is why it helps the parties to control the "purple crayon" to draw the districts to their advantage. Like four-year-old Harold, the party that succeeds in the redistricting process can draw a world that suits them. And in 2012, the Republicans are the party holding the purple crayon.