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Redistricting and its impact on the battle for the House

With less than a month until Election Day, non-partisan political prognosticators -- such as the Cook Political Report and the Rothenberg Political Report -- are predicting that Democrats have a steep climb to take back control of the U.S. House of Representatives.

And there's one reason why, even with the political winds that have been blowing at the Democrats' backs over the past couple of months -- redistricting.

The decennial redistricting process is usually a very partisan affair, in which the political parties do everything they can to take advantage of how the congressional districts are drawn.

Given the Republican Party's electoral success in 2010 -- when it won governor's mansions and turned more than 740 state House and Senate seats red -- the GOP had unilateral authority over the drawing of 202 congressional districts, Democrats had authority over 47, and the others were drawn by a commission or  by governors and legislatures from different parties, according to  the National Conference of State Legislators.

That gave Republicans a big edge in strengthening their incumbents and trying to weaken sitting Democrats, although Democrats did the same in the states where they held the political advantage (notably Illinois and New York).

Here's the current state of play: Democrats must net 25 House seats to wrest control back from Republicans; 218 seats are needed for control.

The Cook Political Report rates 192 GOP-held seats as Solid Republican and 157 Democratic-held seats as Solid Democrat. That leaves only 50 Republican and 36 Democrat seats in the Likely/Lean/Tossup pool.

And if only the "Tossup" seats are considered – or worse – the pool becomes much smaller: Only 15 Democratic-held and 24 Republican-held seats are in this category.