House Ways and Means Committee Chairman Kevin Brady (R-Tex.) says the president’s leadership will be needed to enact a tax package long sought by Republicans. (Melina Mara/The Washington Post)

President Trump’s increasing alienation from fellow Republicans and the business community is further imperiling the party’s top priority for the remainder of the year: cutting taxes and simplifying the byzantine tax code.

Congressional GOP leaders are hoping to recover from their failed effort to replace the Affordable Care Act and salvage their legislative agenda by unifying the party around tax reform, but Trump has spent recent weeks publicly antagonizing key lawmakers and fanning controversy with his response to last weekend’s racist violence in Charlottesville.

Several key lawmakers said Trump will need to focus on selling the GOP’s tax plan when Congress returns in September, and they worried that the difficult job of passing a massive tax package will be nearly impossible without the president playing a key role.

“At the end of the day, President Trump will be incredibly crucial to the success of this,” House Ways and Means Committee Chairman Kevin Brady (R-Tex.) told reporters here Wednesday. “Tax reform is the signature issue of this presidency.”

Brady traveled to the Santa Ynez Mountains near Santa Barbara this week to borrow some inspiration from the last president to rewrite the nation’s tax laws, Ronald Reagan. He and other Republican Congress members stood in front of Reagan’s Rancho del Cielo property and promised to finish their own legislation by year’s end — a pledge Brady said can succeed only if Trump gets on board and stays on board.

President Trump unveiled his tax plan on April 26, after months of pledging to make drastic changes to the tax code. The Post's Damian Paletta explains why tax reform is so complicated. (Jenny Starrs/The Washington Post)

But the call for presidential support comes at a nadir of trust and cooperation between Trump and GOP members in Congress. In the hours leading up to Wednesday’s event, corporate executives and Republican lawmakers were publicly distancing themselves from the president because of his controversial statements assigning blame for violent clashes at a rally in Charlottesville to both the white supremacists who organized the event and those who showed up to protest their presence.

The rush of criticism was the latest in a series of increasingly tense standoffs between Trump and his GOP colleagues. One week earlier, the president launched a multiday assault on Senate Majority Leader Mitch McConnell (R-Ky.) for failing to pass legislation to repeal and replace the Affordable Care Act.

In recent weeks, Republican members have been forced to decide whether they can separate the parts of Trump’s presidency that offend them and their constituents from the reality that his support is likely to be key to achieving their long-sought legislative goals.

While some Republicans say they have grown accustomed to Trump’s often erratic approach to politics, many others are frustrated.

Rep. Carlos Curbelo (R-Fla.), who along with Reps. Peter J. Roskam (R-Ill.) and David Schweikert (R-Ariz.) accompanied Brady on the trip, said that while lawmakers were used to working in “a very distracting environment,” the push for tax reform would require Trump to help re­focus attention away from day-to-day scandal and back to policy details in a way he never did during the health-care debate.

“This is on a whole different scale,” Curbelo said. “The committees are still going to do their work, and it’s not like we’re just going to sit around and talk about issues like this all of the time, but it certainly makes it harder to make a strong case for tax reform to the public because nobody is talking about it.”

Some outside groups have attempted to step into the void left by Trump on tax reform. A number of conservative organizations, including the American Action Network, have launched public relations campaigns touting the benefits of tax reform to voters. The groups are spending millions on advertising, public polling and lobbying to help create momentum for a tax package.

On Thursday, AAN released ­focus-group data that it said showed GOP and independent- leaning voters in Nebraska and California want to see Republicans talk about tax reform. Those surveyed were happy with messages about simplifying the tax code and wanted lawmakers to “specifically illustrate how reform would grow the economy and empower job creation,” AAN said.

But lawmakers have struggled to identify concrete examples of policies that would achieve those goals, including during the event on Wednesday. From the mortgage interest deduction to charitable giving to business expense write-offs, Brady said the plan was still in development and depended on cooperation with Trump.

“We continue to work with the White House, including the president, and the Senate on the details and design of this tax reform,” Brady said when pressed on a plan for taxing international corporations. “We’ll continue to do that through August and after we return as well.”

But congressional Republicans and the White House have yet to agree on much other than the broad strokes of a tax plan.

Instead, Republicans spent a majority of the year locked in a battle over the few specific policies identified in a House tax reform blueprint that was released last year. White House officials and Senate leaders were deeply skeptical of a plan from House Speaker Paul D. Ryan (R-Wis.) that would have cut taxes on exports in an effort to boost U.S. manufacturers.

Ryan and his allies said their proposal would have created more than a $1 trillion in new revenue over 10 years that could be used to offset the cost of lowering tax rates for businesses and individuals. But the plan was met with fierce resistance from key stakeholders, such as retailers, who rely on imports for their business, forcing Ryan to abandon the plan late last month when he joined with Brady, McConnell, Treasury Secretary Steven Mnuchin, National Economic Council Director Gary Cohn and Senate Finance Committee Chairman Orrin G. Hatch (R-Utah) to release a joint statement of unity on taxes.

Trump has failed to build on this show of unity and has instead picked fights with McConnell and other Senate Republicans while stoking public controversies over race.

Brady said Wednesday that he personally could separate Trump’s controversies from the GOP-wide goal of passing a tax bill. “I still think the president has the ability to refocus on tax reform,” he said. “I look to see him pivot to tax reform and jobs and make this case nationwide.”

That pivot was further complicated when Trump was forced to dissolve a pair of corporate advisory groups after a number of CEO members resigned over the president’s comments about the Charlottesville protests.

Business leaders are distancing themselves from Trump, making their role in advancing his agenda awkward at best. They are now likely to focus even more of their efforts on working with Congress in hopes they can enact tax cuts — a desire lawmakers said could help the debate transcend the hard feelings between CEOs and the White House.

Congressional leaders also are holding out hope that the outside pressure will help keep rank-and-file Republicans focused on taxes and eager to avoid mistakes that led to the dramatic failure of their promise to repeal and replace the Affordable Care Act.

“I’m of the mind of the stumbles on health care put a lot of pressure on members to get to ‘yes,’ ” Roskam said, arguing Republican lawmakers see the necessity of nailing down a victory.

“I think most members of Congress are going to say to themselves, ‘I need to go back to a constituency and I’ve got to deliver on health care or taxes,’ ” Roskam said. “The notion of not getting either one of those things done is not a pleasant prospect.”

Brady and his colleagues who assembled in the California mountains this week said they believed the party would unite on taxes in the coming months.

“We’ve got a responsibility as leaders to say, ‘Okay, let’s rub some dirt on our problems and move forward and figure this out,’ ” Roskam said. “It’s bigger than any president.”