NYT:

The second motivation is a concern on the part of A.F.L.-C.I.O. officials thatthe network of conservative philanthropists assembled by Charles G. and David H. Koch is far along in building a sophisticated turnout infrastructure that could give Republican candidates an advantage in November’s elections. These officials note that Americans for Prosperity, a group funded by the Koch network, has hired field staff in numerous states.

Officials at the A.F.L.-C.I.O. believe the asymmetry could be exacerbated by President Obama’s absence from the top of the ballot, who created a cutting edge turnout operation for his campaigns, although other progressive groups have been active in this area.