The party's control of Congress depends in part on Hispanics, a key constituency, voting Democratic

The Dems concerned about losing seats, not must at least policy court the Hispanics on the immigration reform. If they do not successfully pull this off, they are afraid they will lose control over congress. With many open seats, this is not the time to anger this key voting block.
“Hispanic voters have long been frustrated that Obama's campaign promise to pass immigration reform has not been kept. Some members of the House Hispanic Caucus agreed to vote for his health care overhaul on the understanding that he would push immigration reform through this year.”
Now is the time to belly up to the bar!!!