On the individual side, the treatment of state and local deductions remains in question. At least 12 Republicans from high-tax states, whose constituents stand to lose if the tax break is repealed, voted no on the House budget Thursday. The most vocal among them have demanded a compromise on the issue.

Brady said Thursday he hadn’t made a decision on what to do about SALT after meeting with Republicans who are worried that ending the tax break would slam middle-class families in their states -- although he said he’s confident he can accommodate their concerns.

‘Minority Express Lane’

“The bottom line is the ball is in their court, and they know it,” said Representative John Katko, a New York Republican who’s a top target of Democrats in the 2018 election. “They didn’t get specific in this” meeting, he said, but gave “a lot of assurances.”

Democrats, meanwhile, are also waiting to pounce. Brady has so far resisted pressure to embrace Trump’s call for making no changes to the tax-protected status of 401(k) retirement plans. Five Democratic senators -- Debbie Stabenow of Michigan; Sherrod Brown of Ohio; Ron Wyden of Oregon; Ben Cardin of Maryland; and Bob Casey of Pennsylvania -- on Thursday signed a letter warning Republicans against “reducing the opportunities that millions of Americans have to save for their retirement.”

The tax battles will take place amid a mad dash to complete a tax overhaul by the end of the year. House and Senate leaders hope to pass bills through their chambers by Thanksgiving, said Speaker Paul Ryan and Senate Majority Whip John Cornyn. The different bills would then have to be reconciled.

It took about 10 months from when a tax bill was introduced until it was signed by President Ronald Reagan in 1986 -- the last time the U.S. tax code was revamped.

There are, of course, other issues on the congressional agenda. Congress must fund the government to avoid a shutdown by Dec. 8. That could turn ugly as the White House has signaled it’ll demand funding for a border wall, and Democrats say they want a solution to protect young undocumented immigrants. Congress also faces impending business to shore up health-care markets, extend flood insurance and revisit the Iran nuclear deal -- all of which could soak up valuable time.

Nonetheless, there may be some common ground among members of Congress -- a shared interest that could surpass the special interests.

The Republican determination to complete a tax overhaul by the end of the year is driven in part by “the very real and justified fear that the majorities hang in the balance and that failure on tax puts you in the express lane to the minority,” said Rohit Kumar, a former deputy chief of staff to Senate Majority Leader Mitch McConnell who now oversees tax policy for PricewaterhouseCoopers.