Congress returns from its midsummer break Monday for a crucialthree-week stretch that will help determine whether PresidentDonald Trump can deliver on his promise of a historic tax cut.

Several obstacles await lawmakers, including the ongoinghealth-care fight, divisions among Republicans on the basicparameters of a tax bill, and a maelstrom of upcoming deadlines tokeep the government running and avert a catastrophic default onU.S. debt.

Republican leaders had hoped to spend July working on what HouseSpeaker Paul Ryan has called a once-in-a-generation bid to overhaulthe U.S. tax code. But the Senate remains bogged down with thepresident's call to undo Obamacare. With no clear endgame for thateffort, observers question the prospects for tax legislation, whichcan't move procedurally until health care is off the agenda.

“The longer the health-care debate drags out, the harder it'llbe to get to the finish line on tax reform,” said William Galston,a senior fellow at the Brookings Institution. “Health care and taxreform are linked in very concrete ways,” he said, in part becausethe Senate health bill would establish a lower tax base byrepealing a number of taxes imposed by the 2010 Affordable CareAct, or Obamacare.

Meanwhile, House Republicans have been delaying consideration ofa fiscal 2018 budget resolution, the vehicle they plan to use fortax legislation. Factions within the party disagree on whether taxrate cuts for individuals and businesses should be offset with newrevenue or spending cuts, or just be allowed to add to the deficit.Debate among conservative and moderate Republicans has focused onhow deeply they should cut “mandatory” safety net spending.

“There's a train wreck coming,” said G. William Hoagland, asenior vice president at the Bipartisan Policy Center in Washingtonand a former Republican staff director for the Senate BudgetCommittee. “I don't see a tax bill in 2017 at all. Not at all,”Hoagland said. “Not comprehensive tax reform. No way.”

The Republican divisions are “too stark, too great” to pass abudget resolution before the new fiscal year starts in October, hesaid. Hoagland predicted lawmakers will have to settle for stopgapmeasures to keep the government open. “From my perspective and frompast experience, we're very late on everything right now.”

His pessimism stands in contrast to House Speaker Paul Ryan,whose office sent emails to reporters last week proclaiming that“Tax reform is happening. Not next year or next Congress. It ishappening now, in 2017.” The legislation will be“transformational,” Ryan's email said, not “some rinky-dink,watered-down version of reform.”

Lack of Clarity

Republican lawmakers and aides have privately vented that thelack of clarity from Trump on tax specifics has added chaos to thedebate. The only public guidance the White House has released is avague one-page blueprint in April that steered clear of toughquestions like whether a tax cut should be paid for and how.

“We're absolutely committed to getting tax reform done thisyear,” Treasury Secretary Steven Mnuchin said Sunday on ABC's “ThisWeek.” “Our plan is to have a full-blown release of the plan in thebeginning of September, with being able to vote and getting thispassed before the end of the year.”

Mnuchin cited hundreds of meetings on the tax plan so far withHouse and Senate leadership, business leaders, and others. WhiteHouse spokeswoman Natalie Strom added that the private talksare yielding progress, but decisions won't be “hashed out in thepress.”

The House Ways and Means Committee intends to hold twotax-overhaul hearings this month, though neither will involvemarking up actual legislation. One will focus on benefits for smallbusinesses, and another will explore benefits of simplifying thetax code for families and individuals, said the panel's chairman,Rep. Kevin Brady of Texas.

Any more concrete discussions are taking place behind closeddoors. Ryan and Brady, along with Senate Majority Leader MitchMcConnell and Senate Finance Chairman Orrin Hatch, have beenmeeting privately with top administration officials to try to agreeon a path forward for tax legislation. Gary Cohn, Trump's topeconomic adviser, has said officials intend to release a “unified”plan in early September.

By then, after a month-long recess in August, Congress will haveto pass a bill to keep the government funded, extend the Children'sHealth-Care Program, and continue federal flood insurance — all bySept. 30. Calls to cancel the August recess and keep working inWashington are growing within the Republican rank and file, butthere's no indication that party leaders will comply.

By the middle of October, Congress will also have to raise thedebt ceiling, according to a recent report by the CongressionalBudget Office. Past debt-ceiling votes have stirred oppositionamong many Republicans — a further division that may complicate thepolitics of a tax-overhaul vote.

Arthur Laffer, the supply-side economist and cheerleader for taxcuts, says he's trying to remain optimistic. But as Congressreturns to its messy health-care debate, he worries that the issuehas diminished the prospects for a tax bill.

Lawmakers should have just swiftly repealed Obamacare earlierthis year with a delayed enactment — perhaps three or four years —and then moved on to taxes, Laffer said. “Now they're caught init.”

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