Immigration reform advocates still disagree over the Senate’s failed 2007 attempt to push through legislation that would have provided a path to legalization for the estimated 12 million undocumented immigrants in the United States. Unions and big business had briefly allied in supporting a legalization program combined with an increase in visas. But the partnership collapsed after an ill-begotten attempt to secure the bill’s passage, which added so many noxious provisions that it lost many of its supporters while failing to win over implacable opponents.