Mr. Camp has approached the task methodically. Eleven bipartisan working groups last month completed their assessments of tax issues in areas like tax-exempt organizations, education, manufacturing, retirement savings and real estate. On May 6, the bipartisan Joint Committee on Taxation wrapped up a 568-page compendium of options to overhaul the code.

What he lacks, at least so far, is the voter backing needed to propel the effort, which by definition would mean sacrificing or curtailing some politically popular tax breaks, like education tax credits and the mortgage interest deduction. Republican aides say that support, fueled by anger, could be building.

The I.R.S. controversies have trained voter attention on an agency they have long reviled for personal reasons.

A bipartisan group of senators, meantime, have spotlighted the byzantine efforts of Apple Inc. to take advantage of the tax code’s complexity to shield record profits from United States taxation with a web of offshore holdings.