Architects of a revived immigration compromise are directing an intense behind-the-scenes bargaining effort to round up enough votes among wavering Republicans to keep it alive. Senate leaders' announcement Thursday that they would allow the bill a second chance came after getting assurances from key negotiators that they could produce enough support to steer the measure through a procedural minefield, including attempts by conservatives to block it.

The fragile compromise would grant millions of illegal immigrants lawful status while tightening border security and creating new measures for weeding out illegal workers at job sites. Championed by President Bush, it has sparked an outcry among conservatives who regard it as amnesty for lawbreakers.

An agreement to debate the bill again is no guarantee it will be approved. The staunchest critics in the Senate - notably Republican Jeff Sessions of Alabama - predict that growing voter outcry against amnesty will bring wavering opponents back into line. And the bill has not been taken up at all yet by the House, where Speaker Nancy Pelosi says the leadership has its own ideas about what a "comprehensive" immigration bill should include.