Fate of deductions for local taxes and mortgage interest in the Republican tax overhaul bill remains to be determined. (Jonathan Ernst/Reuters)

The political jostling and frenetic lobbying on Capitol Hill over the Republican tax overhaul bill are producing unexpected developments that could prove important to homeowners, sellers and buyers.

The drafting of legislative language is a work in progress behind closed doors, but it appears that there have been some key changes in thinking since the White House and congressional Republicans released what they call their “framework” for the tax bill Sept. 27.

One of the biggest shifts involves deductions of state and local taxes. Republican tax plans have called for a doubling of the standard deduction — to $12,000 for single filers and $24,000 for joint filers — paired with the elimination of a slew of popular write-offs, including state and local taxes.

This “SALT” deduction is among the most widely used in the U.S. tax code, and it includes income taxes, general sales taxes and property taxes. Eliminating it would raise federal revenue by an estimated $1.3 trillion over the coming 10 years. Zeroing out SALT has been a crucial element in the Republican tax framework, which badly needs revenue-raisers to counter deep losses caused by rate cuts for corporations and other taxpayers.

Homeowners, especially in the high-tax corridors of the Northeast and in Washington, Maryland, Virginia and parts of the Midwest and California, are among SALT’s heaviest users. Most of these areas have higher-than-average home prices and household incomes. They tend to vote Democratic but have some Republican representation in the House and Senate.

Those blue-state Republicans, in fact, have been a key force behind the rethinking on SALT. They know that their constituents would be disproportionately affected by a total elimination of the SALT deduction, and they’ve lobbied House and Senate tax-writing committee leaders for relief. Among the possibilities:

●Allowing homeowners to write off property taxes but not income or sales taxes.

●Giving homeowners the choice of either writing off state and local taxes or mortgage interest, but not both.

●Setting a household income ceiling for eligibility to take the SALT deduction.

It’s not clear which, if any, of these might show up in a final legislative package, but the SALT issue is definitely in play. Any of these changes would lower revenue. Limiting SALT deductions to property taxes but not income or sales taxes, for instance, would cost the government an estimated $300 billion over 10 years. But compromising on SALT would solidify political support for the tax plan among blue-state Republicans, whose votes could be essential to passage.

Another noteworthy area where there’s been some rethinking: the mortgage-interest deduction. Under the framework proposal, this popular benefit would be left untouched in the tax code. But doubling the standard deduction would mean that far fewer homeowners would choose to itemize and claim it. As a result, critics say, the deduction would be watered down as a financial spur to home-buying.

The 1.2 million-member National Association of Realtors has been outspoken in demanding that tax writers preserve the effectiveness of the deduction. But in recent weeks, other major housing groups, such as the National Association of Home Builders and the Mortgage Bankers Association, have expressed willingness to explore alternatives — and that has helped spark interest in creating a new form of subsidy: a mortgage tax credit, perhaps in conjunction with a substantial reduction in the current $1 million ceiling on deductions for mortgage interest.

Under the credit concept, borrowers might be able to subtract some percentage — say, 10 or 15 percent — of interest payments off their federal tax bottom line, no matter what their income tax bracket. (Deductions, unlike credits, vary based on tax brackets; the higher your bracket, the bigger your deduction.)

J.P. Delmore, a top lobbyist for the home builders association, told me his group is seeing “serious interest” in the credit idea. “There is a recognition that a properly crafted credit would provide a broad, meaningful tax incentive to millions of middle-class homeowners who do not itemize currently,” he said. In a speech last week, House Ways and Means Committee Chairman Kevin Brady (R-Tex.), confirmed that he is open to reexamining the mortgage-interest deduction, including ways to open it up to “all phases of homeownership.” A credit, which would be available to non-itemizers, would fit that description, say supporters of the idea.

Where’s this all headed? Republican leaders hope to pass their tax overhaul bill before the end of the year. That’s optimistic. But keep this in mind: Whatever happens to the bill, there’s a surprising willingness afoot to reevaluate decades-old approaches to encouraging homeownership with tax benefits while simplifying the tax code.

Ken Harney's email address is kenharney@earthlink.net.