The Republican tax overhaul effort is in for a marathon debateon the Senate floor at the end of this month, with dozens of doomedDemocratic amendments. But the real action will be elsewhere,behind closed doors.

Two parallel and largely private negotiations will determine thecontent of the bill that's due for a full Senate vote as early asNov. 30: One is aimed at getting about a half-dozen wavering GOPsenators on board. The other will attempt to smooth the path for afinal House-Senate compromise in December.

Neither will be easy. GOP leaders must write a bill that canpass under the Senate's strict budget rules while cobbling together50 Senate votes without alienating the House GOP's coalition ofconservatives and moderates from high-tax districts. They'll alsohave to avoid political land mines such as the divisive health-caredebate that has riven Republicans for much of this year.