The health care failure was a major setback to the tax effort, and Mr. Trump’s provocative use of social media has been a distraction for members of his party.

In late July, Mr. Ryan agreed to cast aside the border-adjustment tax on imports that was the centerpiece of his tax-overhaul vision. Since then, lawmakers, lobbyists and businesses have been eagerly anticipating details on a new approach for making good on the promise to cut taxes for businesses and individuals and to move to a territorial tax system, which would largely exclude foreign-earned income from American taxes. In theory, this will all happen without ballooning the deficit.

During the recess, members of the Trump administration worked with Congress to figure out how deep they can reduce tax rates, which deductions to eliminate and how to make the tax code simpler. Intense battles are expected over state and local tax deductions, possible changes to the mortgage interest deduction, any changes to the tax system that benefit the rich and the treatment of taxes for small “pass through” businesses not subject to the corporate income tax.

It remains to be seen whether the eventual tax legislation will be “deficit neutral” and permanent, or whether Republicans will have to settle for temporary tax cuts that lose revenue. Temporary cuts would be a blow to deficit hawks and a significant scaling back of tax-code overhaul that many business leaders say is needed.

Tax-writing committees have been looking at ways to make some parts of the plan temporary and some parts permanent as Republicans continue to assume they will get few, if any, votes from Democrats. For now, they are planning to use the budget reconciliation process, which requires a simple majority in the Senate for passage.

But that comes with its own set of complications.

The House and Senate have yet to even agree upon a budget resolution, which they must do before they can pass a tax bill. Divisions within the Republican Party make it far from clear that this will be possible.

As critical as tax reform is to Republicans, raising the statutory borrowing limit and funding the government are more pressing priorities. At this point, Republicans are considering a three-month continuing resolution to keep the government running and attaching it to a debt ceiling bill. That would buy more time and prevent markets from becoming jittery over the prospect of a shutdown or a default.