According to a Washington Post Election Lab projection from May 2014, an incumbent in 405 of the 435 House contests has a 90 percent chance or greater of winning his or her seat, leaving only 30 seats still relatively up for grabs. Other prominent forecasters, such as the Cook or Rothenberg outfits, have similar predictions that approximately 10 percent of House races are competitive.

These numbers follow a trend that has been seen in recent election cycles. In the 2002 and 2004 elections, a majority of congressional races were uncompetitive, as only 7 percent of the contests were decided by a margin of 10 percentage points or fewer.

Though there are numerous factors that explain the predictability of House elections, such as the durability of incumbents and the partisan advantages Democrats and Republicans enjoy in their respective strongholds, one contributor is redistricting -- or, more accurately, gerrymandering -- by both parties in order to cement partisan hegemony in their states.

Research by ProPublica shows that Republicans launched a concerted effort at redistricting in 2010. That year, Republican strategist Karl Rove published a column affirming that, "He who controls redistricting can control Congress." Also in 2010, Ed Gillespie became the chairman of the Republican State Leadership Committee (RSLC) and made winning state legislatures -- which in many states are responsible for drawing congressional districts -- a national priority.

First, the RSLC and other Republican groups funneled millions of dollars from various corporations and big-name donors to professed tax-exempt and nonpartisan entities. For instance, the RSLC gave over a million dollars to Real Jobs NC, a group led by millionaire conservative activist Art Pope. Real Jobs NC ran ads against 20 Democrats in North Carolina’s statewide election in 2010, which helped Republicans win control of both legislative chambers.

After winning the state legislature, the RSLC gave money through its related non-disclosing entity, the State Government Leadership Foundation, to pay redistricting experts to redraw North Carolina’s 13 congressional boundaries in a more partisan way. North Carolina Democrats were “packed” into three districts, a feature of what the state’s congressional delegation optimistically called the “10-3 map.”

In the following 2012 congressional elections, the state’s delegation changed from 7 Democrats and 6 Republicans to 9 Republicans and 4 Democrats, despite Democratic House candidates receiving 50.5 percent of the vote. In Pennsylvania, the outcome was similar: Democratic House contenders won 83,000 more votes statewide but sent 5 Democrats to the House compared to the Republicans’ thirteen.

All in all, the RSLC’s so-called REDMAP project was a national success. It raised $30 million and helped Republicans win 12 legislatures responsible for drawing the district lines for 40 percent of the House’s seats.

During the 2012 elections, GOP candidates in Republican-controlled states won nearly three-quarters of the state's congressional seats (72%) with slightly more than half (53%) of the vote.

These results compare to those in Democratic-controlled states, some of which also control redistricting. In 2012, Democrats won 71 percent of the available seats in their states with 56 percent of the vote.

Control over the redistricting process allowed them to keep Republicans disproportionately unrepresented in Congress. For instance, in Illinois, Republicans won 45 percent of the vote, but just one-third of the state’s House seats.

Nevertheless, despite Democrats winning more than 1.1 million more votes nationwide, Republicans retained control of the House and even expanded it through a combination of tea party influence and successful redistricting.

In states where courts, nonpartisan commissions, or divided legislatures redrew the boundaries, the discrepancy between the percentage of votes and seats won was significantly narrower. In these states, Republicans won 46 percent of the vote and 44 percent of the seats.

In recent years, several states have moved to remove partisanship from the redistricting process. In California, for instance, congressional redistricting is now securely in the hands of an outside commission, and Florida no longer allows its electoral borders to be redrawn in a way that secures either party a competitive advantage.

On July 11, 2014, a federal judge in Florida rejected the state legislature's redistricting plans on the grounds that "Republican political consultants or operatives did in fact conspire to manipulate and influence the redistricting process" and thus violated the state's Fair Districts constitutional amendment. It is unclear whether the legislature will have to redraw the boundaries for the state's 17 congressional districts before the 2014 midterm elections.

Members of Congress have also sponsored bills to reform redistricting; however, neither party has shown mass support for such measures. GovTrack, for instance, gave H.R. 278, the "John Tanner Fairness and Independence in Redistricting Act," a mere one percent chance of being enacted in 2013.