In a memo issued by the Democratic Congressional Campaign Committee, communications director Jesse Ferguson outlines four ways in which the new Cook Partisan Voting Index (PVI) scores show that Democrats can be competitive, and that "many assumptions made about a limited 2014 battlefield have been proven untrue."

Democrats face the difficult task of flipping 17 Republican-held seats to take back the majority, and earlier this year expressed caution when handicapping their chances going into 2014.

But the memo notes that Obama won 17 Republican held-seats, potentially making those ripe for Democratic challenges. Democrats also believe they have a battlefield of 51 Republican-held seats to pursue, all swing seats with a competitive partisan voting index.

And the memo pushes back against the belief, coming out of the 2012 election, that redistricting has delivered Republicans a steadfast majority for the next decade. The number of swing seats has shrunk by 13, but the memo says that's not "significantly different" than before redistricting.

It adds that the number of solid Democratic seats has increased, while the number of solid Republican seats has decreased.

"…These numbers make it plain — 2014 will be an incredibly competitive election year, and Republican hopes that redistricting would give them an impenetrable majority were nothing but fantasies," Ferguson writes.

However, Charlie Cook himself notes in the new PVI rankings that redistricting has complicated Democratic efforts to take back the House, as it clustered Democratic voters and overall, vastly more House seats are more Republican than more Democratic

National Republican Congressional Committee spokesman Daniel Scarpinato said the new Cook scores actually proved Democrats will have a tough time taking the majority.

“We knew the Democrats were bad at arithmetic, but apparently they can’t read either. This latest analysis is actually just more proof that they face a daunting map, especially with Barack ObamaBarack Hussein ObamaAll five living former presidents to attend hurricane relief concert Overnight Health Care: Schumer calls for tying ObamaCare fix to children's health insurance | Puerto Rico's water woes worsen | Dems plead for nursing home residents' right to sue Interior moves to delay Obama’s methane leak rule MORE and Nancy Pelosi teaming up as their national ticket," he said.

Democrats will need to defend every Democratic-leaning seat, and also win 30 Republican-leaning seats, to flip the House.