Short version: Alaska, Louisiana, and North Carolina to Toss-Up: New Hampshire to Lean Democrat. To be fair, Cook is also degrading GA to Toss-Up and put Mississippi into Likely Republican territory, but the map is still bad for Democrats, and frankly just got worse for them. But this may be the most important bit:
Democrats have put together what they say is effectively a presidential campaign effort focused solely on these competitive races that will bring the same kind of field organization and utilize data analytics and other resources in much the same way that the Obama campaign did in 2012. The goal is to boost Democratic turnout above both the 2010 and typical midterm election levels into something closer to a presidential level turnout among key groups, though they acknowledge the impossibility of truly replicating turnout levels that high.
At the same time, Republicans are putting together national party-driven field operations unlike any they have ever done before. They already have 15 staff on the ground in Alaska. Even though they won’t know who their incumbent will be until after the August 19 primary, they can hit the ground running with a turnkey organization in place.
The problem here for Democrats is that they did not actually win Alaska, Arkansas, Georgia, Kentucky, Louisiana, Mississippi, Montana, North Carolina, South Dakota, or West Virginia in 2012. In fact, the Democratic percentage of the vote in most if not all of those states was lower in 2012 than it was in 2008. At this stage, the Democratic party pretty much has to do everything right to keep the Senate. This represents a small but noticeable change from the height of the last government shutdown, and it’s not a change in the Democrats’ favor.
And it’s only March.