In October 2016 then-Republican presidential candidate Donald Trump was joined by his family at a ribbon-cutting for the Trump International Hotel in Washington, D.C., a project that transformed a classic post office into luxury lodging and benefited from a federal tax credit for the rehabilitation of historic properties that the Reagan tax reform of 1981 embraced. The fate of that historic tax credit remains uncertain in the current GOP tax plan, which the Senate hopes to push through before week’s end.

The House removed the tax credit entirely from its bill, while the Senate has added a version of it back into its tax-reform language, though in a potentially weakened form and one that is still subject to alteration.

For small-town entrepreneurs like Jason Duff, a real estate entrepreneur from a county in the swing state of Ohio, where Trump received 76 percent of the vote last November, this tax irony is hitting hard: “I am really impacted by the disappearance of the 20 percent federal historic-building tax credit,” Duff said.

His company, Bellefontaine Ohio Properties — which operates stores, restaurants and other real estate — takes the risk of rehabbing old buildings on Main Street, and it’s a risk the tax code has encouraged over the past four decades.

“There’s tons of evidence here on Main Street, from many who bought historic businesses, that it has really benefited their communities,” Duff said.

The GOP tax-reform plan has included a narrative about wiping away tax benefits that have accrued for residents of blue states and affluent cities, but the historic tax credit (HTC) — which to date has facilitated the rehabilitation of more than 42,000 certified historic buildings and has attracted more than $84 billion in new private capital to the historic cores of cities and towns across the nation — is not a partisan issue. It is, on the other hand, important to entrepreneurs and investors revitalizing urban districts of former industrial towns and cities, as well as small towns across the country.

“It has not gotten enough attention relative to its size,” said Brett Theodos, a senior research associate at the Urban Institute. “[HTCs] are not red- or blue-state things.”

Duff recently purchased three buildings in Bellefontaine that are slated for renovation in 2018, including an abandoned old theater where lines in the late 1930s stretched down the block. “If the historic tax credit is not put back in legislation, these projects are in jeopardy. … Right now I’m stopping conversations with architects and engineers, and uncertainty is probably the biggest fear,” Duff said.

The Midwest communities that helped deliver the presidency to Trump are peppered with these properties, and while malls are really struggling, “Main Street is coming back back strong,” Duff said, helped by entrepreneurs investing in buildings that create urbanlike environments.

“We are Trumpland,” Duff said of his Logan County, Ohio. “I am seeing unemployment in our community nearing a record low, and I am the most optimistic about the local economy that I’ve been in 10 years, but we do have issues with opioid abuse and retraining and preparing workers for the future. There is a lot in the tax code that, from a policy standpoint, when designed correctly, can fix these costly problems.”

Nan Whaley, the Democratic mayor of Dayton, Ohio, put it more bluntly: “For midsize cities like Dayton, HTCs are the avenue, not one avenue” for how these urban revitalization projects are financed.

The old Dayton Arcade complex of seven buildings in the city center has been vacant since 1992 and is currently under redevelopment, but the mayor said, “If the HTC goes, it’s over.”

Whaley said there is no other place to find the capital for the project other than entrepreneurs who depend on the tax credit. As a result, it could cost the city $12 million to demolish the Arcade rather than redevelop it. Worse, most spaces where historic buildings are demolished will not be developed again, because the uniqueness of the space is part of the attraction for investors aiming to bring in consumers to new businesses, as well homebuyers and renters for downtown residential properties.

Dayton was No. 1 in the nation last year in the percentage of residents under 35 who bought homes (41 percent), Whaley noted. “It’s not only the cost of investment. … You lose the spin-off of the young people moving back to the urban core. We are seeing that in Dayton for the first time in 50 years.”

According to data from the Ohio Mayors Alliance, Dayton has utilized 17 federal historic tax credits totaling $67 million.

Ohio ranks third among states in the number of projects completed using the HTC, according to data from the National Trust for Historic Preservation, behind Missouri and Virginia. Cities that have made the greatest use of the HTC to spur redevelopment of urban cores include many former industrial and mill towns, such as Cincinnati, St. Louis, New Orleans, Richmond, Cleveland, Durham, Greensboro and Baltimore.

But 40 percent of projects are in communities with 25,000 or less, according to the National Trust for Historic Preservation. Whaley said that for smaller towns the value of the tax credit to the community can be transformative. “That’s what is most concerning,” Whaley said. “For our communities having really tough times, these historic tax credits hold an identity in place while allowing the community to position for the future.”

There are actually two historic tax credits for rehabbing old buildings, and for small town entrepreneurs like Duff, the loss of the smaller of the two — a 10 percent historic tax credit killed in both current House and Senate versions — will hit some of the most neglected areas of the country most in need of redevelopment the hardest. The 10 percent tax credit for buildings that predate 1936, but without true “historic” classification other than date of build, has fewer requirements and gets projects to completion quicker. The larger 20 percent tax credit is less critical in a town like Duff’s Bellefontaine (population under 20,000), where property prices are low and the financing gap for real estate entrepreneurs is smaller than in cities.

The use of the HTC is at its highest levels of use and growing, according to data from the Urban Institute. In 2016, use of HTCs experienced the largest year-over-year increase since 1986.

Merrill Hoopengardner, president of the National Trust Community Investment Corp., a for-profit affiliate of the National Trust for Historic Preservation, said private lenders struggle with investing in historic properties, and even with the 20 percent tax credit there is often still a gap in funding. Costs to rehab historic properties are higher than for new developments, and they often are in lower-income areas — 60 percent to 75 percent of these projects. Where business success is less assured, it is harder to attract workers, and rents may need to be reduced to encourage migration of start-ups and individuals.

“What we hear from developers is that the HTC is a floor for the amount of money they need, and almost every HTC project has to scramble to find other flexible sources of funding,” Hoopengardner said, adding, “The gap can be 40 percent.”

The Senate Budget Committee voted on Tuesday to send the tax bill forward, moving it one step closer to a floor vote this week. The Senate’s original bill cut the 20 percent tax credit in half but later restored it to 20 percent through an effort headed by Louisiana Republican Bill Cassidy, though with the requirement that it be taken over five years (4 percent annually).

“We’re not slowing down in advocacy at this point,” said Shaw Sprague, senior director of government relations at the National Trust for Historic Preservation. “There are several steps to go.”

Hoopengardner said developers are still trying to do the math on how the spreading out of the credit over five years would influence their investing decisions. There is obviously greater value in a 20 percent tax credit that can be taken all at once, and after a building has already made the investment and turned the lights on for its new purpose. But she said that new Senate language is still better than the earlier version, which she described as “unworkable and insufficient.”

There will always be winners and losers within specific industries in a major overhaul of the tax code, and most small-business groups continue to support the overall GOP effort for simplifying the tax code and reducing the number of brackets. Small-business lobbies have also been most focused on the need for greater tax relief at the level of the pass-through business structure that dominates the entrepreneurial landscape.

Duff said many of the entrepreneurs he speaks with are excited about the tax reform effort, and the reduction in brackets and lower overall effective rate, which will put more cash in their pockets.

When asked how they would invest extra money from a tax cut, the largest group of small-business owners (46 percent) said they would invest it, ahead of “save it” (44 percent) and “spent it” (32 percent), according to 1,290 small-business owners surveyed in mid-November by the CNBC/SurveyMonkey Small Business Survey.

More than half (53 percent) of small-business owners think cutting the corporate tax rate will help businesses create jobs, according to the CNBC/SurveyMonkey Small Business Survey. Fifty-six percent think cutting the corporate tax rate will stimulate economic growth. But they don’t think small business will be the biggest beneficiary of the GOP plan.

“Doing away with all those brackets is a win, but the [HTC] is negative impact on my business operations even with simplified brackets,” Duff said. “People really need to be taking the time to understand how this bill will impact them,” he said. “If you want to change behavior that encourages people to save and invest and make smart business decisions you need to take the track record of HTCs into consideration and they do make sense.”

Nerves are running high among mayors. Whaley said that the mayor of Hamilton, Ohio called her in a panic because of what the HTC has done for Hamilton, a town of roughly 60,000 which is located close to the setting of “Hillbilly Elegy,” the memoir by the venture capitalist J.D. Vance about growing up in rural America that was viewed as prophetic in the wake of Trump’s election.

There is academic research on what the HTC has meant to community development commissioned by the National Trust for Historic Preservation and National Park Service. It estimated that between 1978 and 2016 (the life of the HTC program), tax credit projects generated $29.8 billion in federal taxes, exceeding the $25.2 billion in credits allocated.

“Trying to simplify [the tax code] may hurt in that some programs are working,” Duff said.

There is no academic research on what would happen if the HTC disappeared, though after the 1986 tax reform reduced the deduction from 25 percent to 20 percent, usage did decline.

“The great thing about HTCs is it has the federal government saying to older communities that they have value and are meaningful to the future of our country,” said Whaley, who announced her candidacy for Ohio Governor in May at a craft brewery built on the site of a 1930s iron and glassworks foundry. “Usually the federal government doesn’t help at all, but now they’re interested in harming.”

Hoopengardner said there are still opportunities for changes that improve the HTC, or “other changes.”

“The treatment we had in the House could prevail,” she said. “We consider it all hands on deck until it’s signed into law.”