Details leaking out about the Republican tax reform plan hint that while two popular deductions would remain intact, they’d become useless to the majority of taxpayers who now take advantage of them.

GOP lawmakers have signaled they’ll retain the tax breaks for mortgage interest and charitable contributions even as they pursue eliminating others.

Yet given Republican leaders’ intention to nearly double the standard deduction, “many current itemizers would choose that instead, so a lot less people would use those deductions,” said Joseph Rosenberg, a senior research associate at the Urban-Brookings Tax Policy Center.

Currently, taxpayers choose between the standard deduction or itemized deductions and use whichever amount is greater to reduce their tax bill. For 2017, the standard deduction is $6,350 for individual taxpayers, $9,350 for heads of households and $12,700 for joint filers.

In other words, if those amounts nearly double as discussed by both the White House and congressional Republicans, a married couple would need deductions to exceed $24,000 to make itemizing worthwhile.

The Tax Policy Center estimates that of the 45 million tax filers who itemize, 38 million, or 84 percent, would opt for the $24,000 standard deduction because it would exceed the combined value of other deductions available to them.

President Donald Trump is expected to deliver a speech Wednesday in Indianapolis that will offer more specifics about what plan will emerge in Congress, although it’s unclear how detailed the reveal will be.

The deductions for mortgage interest and charitable contributions have been a political third rail in the past, due largely to the idea that they spur home ownership and charitable giving. Yet of all taxpayers, only about 20 percent take advantage of each deduction for mortgage interest and charitable contributions, according to the tax policy center.

Of the roughly one-third of taxpayers who do itemize, roughly three-quarters use each of the deductions. The biggest benefits tend to go to higher-income taxpayers.

For instance, the 7.18 million filers with incomes of $200,000 or more will reduce their taxable income by $29.78 billion this year from using the mortgage interest deduction, according to tax expenditure estimates from the congressional Joint Committee on Taxation.

In comparison, the 14.6 million filers with incomes of $100,000 to $200,000 will save less: $24.85 billion. Filers with incomes below that have even smaller tax savings.

Likewise, the 8.2 million filers with incomes above $200,000 will save a collective $40.7 billion this year by using the charitable deduction. The 15.2 million filers with incomes of $100,000 to $200,000 will reduce their tax bill by $11.9 billion.

Nonprofit groups and the home building industry are concerned about what reduced utilization of those deductions would mean for home ownership and charitable giving.

“It marginalizes the mortgage interest deduction,” said J.P. Delmore, assistant vice president of government affairs for the National Association of Home Builders. “We’d see the effect where a small number of homeowners would benefit, and that’s not the direction anyone is looking to go with tax reform.”

The National Association of Realtors also has expressed concern that home prices would suffer if the mortgage interest deduction were to become useless to most homeowners.

The group released a study in May showing that if elements similar to GOP’s 2016 plan went into effect, home values would fall by more than 10.2 percent on average in the near term.

The study also found that homeowners with income of $50,000 to $200,000 would face an average tax increase of $815 while non-homeowners in that range would get an average tax cut of $516.

“This is an emerging issue [lawmakers] don’t intend to create,” Delmore said. “But we hope there’s an opportunity to find a solution so that homeowners have a meaningful tax incentive that doesn’t involve being marginalized and benefiting only the wealthy.”