Republican leaders in Congress have been hesitant to raise tax rates on anyone because the party’s brand is largely built around the idea that the economy does best when people have more money to spend. Yet they may have no choice: Senator Susan Collins, Republican of Maine, said this week that she opposed lowering the top tax rate for individuals earning more than $1 million, creating pressure for Republicans to include a higher bracket in order to win passage.

Making some cuts temporary or gradual

Republican lawmakers are selling their plan as a middle-class tax cut, and the bill is expected to create three income tax brackets — 12 percent, 25 percent and 35 percent — and call for doubling the standard deduction. Yet lawmakers are considering making these changes temporary, so they would expire after 10 years.

The conventional wisdom is that a future Congress will vote to continue the cuts and not allow them to expire. But that’s a tricky assumption given their cost, which will only exacerbate a federal deficit already on an upward trajectory. The Treasury Department said the deficit for the fiscal year 2017 grew by $80 billion, to $666 billion. Federal debt, which has already topped $20 trillion, is expected to grow by an additional $10 trillion over the next decade, according to the Congressional Budget Office.

Compounding the math problem is that the plan would probably make the corporate tax cuts permanent. Lawmakers argue that a permanent cut, to 20 percent from today’s 35 percent rate, is needed to trigger the economic growth they anticipate, and they say it will ultimately put more money into workers’ pockets.

Still, those corporate tax cuts are expected to cost $2 trillion over the next decade and, to help make the budget work, lawmakers are discussing phasing in the corporate tax cut over several years to get to the 20 percent rate. The White House on Monday seemed to suggest that was a nonstarter.

Limiting the estate tax

The original framework called for repealing the estate tax, which would reduce federal revenues by $239 billion over a decade.

Estates are taxed at a rate of 40 percent, but the first $5.49 million of an inheritance is exempt from taxation. Couples can leave their heirs as much as $11 million, none of it taxed, meaning only a few thousand wealthy estates are subject to the tax each year.