Alex Boris, President of the Yeshiva University Democrats, spoke to CampusJ about today’s election. “I can only tell you in comparison to last year that students are much more active on campus, which I am very excited about,” he said.
The YUD were going to assist the Dave Mejias for Congress campaign, where polls showed a close race. Lack of interest led them to cancel the trip.
Boris commented on the YUR’s campaign for Santorum:

I actually find it amusing that the YU Repubs took students to Philadelphia this week, because, to put it quite frankly, it’s like throwing themselves in front of the Titanic. The National Republican Committee and the National Republican Senatorial Committee have both refused to reserve time at Pennsylvania television stations for “independent expenditure” ads supporting Santorum. The Republicans themselves don’t even think that this man stands a chance. I’m worried about all the students that are finally getting active (going down to the Santorum campaign) and will not be able to reap the benefits of their hard work. The whole deal was more for show than anything else.

As of this posting, the Pennsylvania race has been called for Casey over Santorum.
As to why YUD cancelled the trip:

Unfortunately, signs that I personally put up around campus were torn down and there were very little responses to the emails sent out. We were still going to go down with a small group, but there were scheduling conflicts.