Why a $10,000 Deduction Is Blocking the G.O.P.’s $3.8 Trillion Tax Bill

A year ago, as New York Democratic groups strategized about how to connect with voters in an up-for-grabs special House election on Long Island, they expected Israel to be a major talking point and prepared accordingly.

But all voters wanted to talk about was their high tax bills.

The pivot came quickly. Gabby Seay, a Democratic organizer with Battleground New York, recalled how canvassers were given talking points about how the Democratic candidate, Tom Suozzi, supported lifting a $10,000 cap on SALT deductions — the amount of state and local taxes that can be written off on federal tax returns.

“Most voters cannot talk about taxes with sophistication because it’s complicated,” she said. “But not SALT. It is part of the ethos of Long Island and the suburbs writ large. Voters remember when you take money out of their pockets.”

The SALT deduction has become an outsize stumbling block for Republicans trying to pass a $3.8 trillion tax proposal that would extend President Trump’s 2017 tax cuts and roll back subsidies for clean energy, among other things.

A group of Republican House members, mostly from New York, New Jersey and California, have vowed to vote no on the package unless the cap, which helped pay for the 2017 cuts and expires this year, is raised or abolished. And even among the holdouts, there is dissension — something that drew attention on Tuesday night during a Republican caucus meeting with Speaker Mike Johnson.

Some of the New York congressmen representing suburban districts, including Representatives Mike Lawler, Nick LaLota and Andrew Garbarino, asked that their colleague, Nicole Malliotakis, leave the meeting. Ms. Malliotakis represents a New York City district and supports raising the cap to $30,000; her colleagues want it abolished or raised significantly further.