There are several reasons why tax-policy experts have been eager for Washington to revamp the tax code, which is not only bloated with benefits, but also so complicated that the typical family spends many hours or hundreds of dollars on a filing that the IRS could probably do itself.

But the practical reasons for tax reform in 2017 are procedural. This gets complicated quickly, but basically, since Democrats probably won’t vote for a large tax cut, the GOP needs a bill that can pass with simple majority—51 votes. Sounds easy enough. But under so-called reconciliation rules, the new law cannot raise the deficit in the long run. As a result, the GOP has to make a choice: either follow George W. Bush and pass a tax cut that expires after ten years, or follow Ronald Reagan and pass a more comprehensive overhaul whose changes have no expiration date.

But writing a tax policy that doesn’t increase the deficit requires the Republican Party to resurrect an ancient and long-forgotten budgetary maneuver known formally as “offsets” and more colloquially as “actually raising revenue in order to pay for stuff.”

There are several ways for Republicans to save money, but the first and easiest solution has disappeared. Repealing Obamacare would have cut hundreds of billions of dollars of taxes on the rich, none of which would have to be offset in the new tax law. Second, Paul Ryan and some Trump advisers have argued for a border-adjustment tax, which would essentially tax importers, and exclude exporters, to help domestic producers. The policy would raise hundreds of billions of dollars to pay for rate cuts. But retailers like Walmart that rely on cheap imports will fiercely oppose the law, and it’s unlikely that the idea will attract a simple majority of Republicans in the Senate.

Third, the most common formula for tax reform is to “lower the rates and broaden the base,” which means cutting marginal tax rates and partially paying for the lost revenue by eliminating tax benefits. Paul Ryan’s most recent tax reform would scrap most itemized deductions, except for those for mortgage interest and donations to charity. That means junking at least 70 tax benefits in the corporate and individual income-tax codes, according to the Tax Policy Center. Removing even one of these is like sending the equivalent of a bat signal into the Washington sky, all but ensuring that lobbyists for that particular cause swarm Capitol Hill or at least send several pointedly worded emails to concerned parties.

The corporate income-tax overhaul, for example, would probably cut the overall rate but also eliminate several benefits for energy companies, such as those for coal production and mining. One can already hear the cries about Trump’s shattered Appalachian promises harmonizing with the agonized moaning of the oil lobby. But the screaming over changes to the individual tax code could be far worse. The Ryan plan removes benefits for injured veterans, people living in low-income housing, foster homes, and families of public-safety officers killed in the line of duty. Pissing off powerful energy conglomerates, infuriating veterans, or endangering orphans, individually, is one thing. To achieve all three in the same bill is an almost impressive feat of anti-populism.