Breitbart: “Senate Democrats know they may lose their last congressional tool to block legislation from the GOP-led Congress in November 2018, because they must defend 23 Seats seats while the GOP need only defend eight seats.
That leaves many of the 23 Democratic Senators — and their leaders — with the difficult task of balancing party solidarity and personal political survival. Party leaders commonly give vulnerable senators leeway to buck their party going into an election year, but if the Democrats allow a third of their senators to freelance on critical votes during the next two years, they cease to function as a party at all.”
Dem seats up in 2018:
9 are rookies, Baldwin, Donnelly, Heinrich, Heitkamp, Hirona, Kaine, King, Murphy, and Warren.
4 won in states which elected Trump.