Makes sense on several levels.
1) They believe that Obama screwed them by failing to deliver on Card Check and by tepid support in Wisconsin. If they don’t deliver some clear punishment now double-dealing Democrats will just go on screwing them.
2) Things are going to start getting very bad for the union leadership in the wake of Wisconsin. Their rank-and-file is going to be under constant pressure of layoffs and/or givebacks. Better to point the finger of blame at the Mormon Republican Millionaire in the White House when that all starts hitting the fan.
3) The money that used to go to Democrats will frankly be needed to cover overhead expenses (i.e. perks for the union bosses) as dues receipts plummet after Wisconsin.
Here’s another take. How much of this decision was prompted by the pull-out of mandatory contributors in Wisconsin?
The AFL-CIO might be under some internal pressure to appease the more moderate members and to keep them in the fold. They might see a possible domino effect happening after having their heads handed to them in WI. A 60% drop in membership has to get their attention.