House Republican seats Cook deemed more in danger include those occupied by Rep. Justin Amash (R-MI), Rep. Tim Walberg (R-MI) and Rep. Tom Reed (R-NY).
The Cook statement warned that while Democrats have acheived fundraising success recently, they still have a while before the 2014 elections.
"Democrats still have a very uphill climb to a majority, and it's doubtful they can sustain this month's momentum for another year," the Cook statement says. "But Republicans' actions have energized Democratic fundraising and recruiting efforts and handed Democrats a potentially effective message."
Updated Friday at 12:24 p.m.