For now, Republicans sidestepped divisions within the party by voting 216-212 to permit them to begin work on a $1.5 trillion tax cut without fear of blocking tactics by Democrats. The legislative landscape is strewn with land mines, however, as GOP tax-writers pick winners and losers among interest groups, business sectors and rank-and-file voters.

The tax bill is the top item on the GOP agenda and would be Trump's first big win in Congress. Republicans hope it would provide a much-needed jolt for the party's political fortunes in advance of next year's midterm elections. Republicans view passage of the upcoming tax measure as a once-in-a-generation opportunity, and its importance has only grown since the party's debacle on health care.

The goal is a full rewrite of the inefficient, loophole-laden tax code in hopes of lower rates for corporations and other businesses and a burst of economic growth. But evidence is growing that some of their hoped-for bold steps — such as eliminating the deduction for state and local taxes — will be replaced by half-measures dictated by politics and a narrow margin for error.