According to CQ, Byron Dorgan and Barbara Boxer are planning to put forward an amendment to strip the temporary guest-worker program from the Senate immigration bill. The guest-worker bit seems to be the main point of contention for many Democrats and labor organizations (e.g.), and if it survives, conservative opponents may be able to find enough allies on the left to sink the bill entirely.
(On the other hand, a Hill staffer tells Kathryn Jean Lopez that, if the guest-worker provision gets taken out, many of the bill's Republican supporters would defect.)
--Bradford Plumer