Steam billowed from the coal-fired Merrimack Station in Bow, N.H. President Trump is ready to dismantle an order by his predecessor that discourages coal-driven power plants.
Jim Cole/Associated Press/File 2015

Steam billowed from the coal-fired Merrimack Station in Bow, N.H. President Trump is ready to dismantle an order by his predecessor that discourages coal-driven power plants.

WASHINGTON — Picking themselves up after the bruising collapse of their health care plan, President Trump and Republicans in Congress will start this week on a legislative obstacle course that will be even more arduous: the first overhaul of the tax code in three decades.

Trump’s inability to make good on his promise to repeal the Affordable Care Act has made the daunting challenge of tax reform even more difficult. Not only has Trump’s aura of political invincibility been shattered, but without killing the Affordable Care Act, Republicans will be unable to rewrite the tax code in the sweeping fashion that the president has sought.

The grand plans of lower rates, fewer loopholes, and a tax on imports may have to be scaled back to a big corporate tax cut and possibly an individual tax cut.

A lot of people think Trump might go for this to get an easy win.

“They have to have a victory here,” said Stephen Moore, a Heritage Foundation economist who advised Trump during the presidential campaign. “But it is going to have to be a bit less ambitious rather than going for the big bang.”

Administration aides signaled Sunday that the president will now seek to build support among moderate Democrats to help push his legislative proposals through Congress, including taxes.

‘‘I think more so now than ever, it’s time for both parties to come together and get to real reforms in this country, whether it be taxes, whether it be health care, whether it be immigration, whether it be infrastructure,’’ White House chief of staff Reince Priebus said on “Fox News Sunday.’’ “This president is ready to lead.’’

Also this week, the administration will issue an executive order that will begin to dismantle a rule issued by former president Obama that sought to slash carbon dioxide emissions and discouraged coal-fired power plants, said Scott Pruitt, head of the Environmental Protection Agency.

“The executive order is going to address the past administration’s effort to kill jobs across this country through the Clean Power Plan,” Pruitt said Sunday on ABC’s “This Week.” He said the president is expected to sign the order Tuesday.

For any tax overhaul proposal, Republicans may have little choice but to scale back the scope because of the arcane rules of lawmaking in Congress. If Republicans intend to act again without the help of…