Republicans, who control only 52 seats in the Senate, plan to use congressional budget rules that allow for approving a tax bill with a simple majority. But those rules also require that tax cuts would have to be offset so they don’t add to the long-term budget deficit. Changes that did increase the deficit would have to expire over time.

Washington Lobbyists

Beyond vague references to eliminating special breaks, the only one that’s been targeted publicly is the state and local tax deduction for individuals. Officials have said they’d preserve deductions for mortgage interest, charitable giving and retirement savings.

“What we’re proposing on the individual side is get rid of the loopholes, get rid of the carve-outs,” Ryan said last week during a CNN town hall. “Just lower people’s tax rates. Let you keep more of your own money.” He offered no additional details during the hour-long event.

The lack of specifics has kept Washington lobbyists on the sidelines -- but that could change as soon as tax writers target any treasured loopholes.

For example, the influential National Association of Realtors wants to retain the state and local tax deduction. Yet the group hasn’t formalized a budget for that fight or other tax-related efforts, said a person familiar with its strategy. The vague plans and difficult legislative calendar present such large impediments to tax legislation that any tactics beyond the usual meetings with lawmakers haven’t been necessary, the person said.

‘Potholes And Sinkholes’

Similarly, there’s been no announcement of a specific tax rate that would be applied to more than $2.6 trillion in profit that U.S. companies have stockpiled overseas. Cohn said in the FT interview that a specific “repatriation” rate on those offshore earnings hadn’t been discussed. (He and Mnuchin said they would be discussing a rate with the House and Senate four months ago when unveiling the White House’s one-page tax plan.)

Details or no details, Cohn hasn’t swayed from saying he’s committed to a full overhaul, listing it as his first, second and third priorities during a Bloomberg TV interview this month.

That level of determination among key players means a tax bill is still possible, said Kevin Madden, a Republican communications strategist who worked for former House Speaker John Boehner. "There’s a reason Kevin Brady and Paul Ryan are criss-crossing the country, talking to workers, talking to businesses both big and small that are major employers."