If Upchuck came out and said, "I can't vote for it," he'd carry along a bunch of others. The fact that he's not going to vote for it, but isn't coming right out and saying so, is his way of having his cake and eating it too. Thanks justiceseeker93.
As things stand now, the Senate and House will vote straight up to disapprove the treaty. Obama will then veto that "legislation," which would send it back for a veto override. Even if Schumer decides to vote for a veto override (i.e., against the deal), I would have to disagree with you that enough other Senate 'Rats will follow Schumer's lead. A vote for a veto override would be a vote against both Obama and against HRC. There's just not enough dissidents in high places in that party.