That is one reason; the other is to pander to their rabid LLL base that have been inundating the Senators with fax and e-mail over the weekend. They rant on about how "If Alito is confirmed this nation will disappear as we now know it - whahahahahahah."
I think you're both right. Isn't it interesting the Democrats are reduced to delaying a vote as a sign of their power? They are not in control of the Presidency, the House or Senate, and are losing their control of the Supreme Court. So now, a delay is considered a win for them. Pathetic pandering to their far left base is what it's all about.