The GOP picked up 63 seats in the House and six in the Senate. And that was horrible. But the real damage was done at the state level, where they picked up 680 state legislative seats and 29 of the 50 governorships, including in key states such as Ohio, Florida, Michigan and Pennsylvania. They also held absolute control in half the state legislatures.
Thus, Republicans were able to not just solidify their control of the House, where they maintain a 33-seat advantage despite losing the House popular vote by one point in 2012, but they locked in control of myriad state legislatures. And you can just scroll down this site to see the damage those wingnut legislatures are wreaking across the country. Thus, we can't allow a repeat of 2020. Republicans are on the wane. The only way they can retain power is via voter suppression or gerrymandering. We must deny them both those options.
As you can see with this map, most states still redistrict via state legislatures, subject to a governor's veto. We have found the last few cycles that when a state deadlocks on drawing boundaries, a fair map designed by judges ends up benefiting Democrats, and even if it doesn't, fair is fair. So gaining the ability to merely block a map is generally a net gain for us.
Winning back heavily gerrymandered state legislatures is not always impossible, but is far more difficult than merely winning back governorships. So how are races in 2014 relevant to 2020? It's all about the power of incumbency.
Learn more about the power of incumbency below the fold.