Should President Trump announce this week that he will "decertify" the Iran nuclear deal he has derided as a historic "embarrassment" to the United States, he in effect would be passing along to Congress responsibility for the fate of the international accord.

In so doing, Trump would be taking a page out of his playbook: Make a showy declaration of transformational change that excites his political base, which is hungry to disrupt the status quo, even if the substance of the move is incremental or indeterminate.

With examples including the Paris climate accord, the domestic opioid epidemic, the U.S.-Mexico border wall and various trade agreements, Trump's actions have not fully lived up to his rhetoric.

The president's flashy pronouncements have masked the more nuanced reality of governing, as actions can take months or even years to be implemented or still require decisions by other stakeholders, such as Congress.

For Trump, the result is politically advantageous. He gets credit from his base for bold action — for withdrawing from the Paris accord or declaring opioids a national emergency — while the policies themselves end up being delayed or punted, in part because of complexities in the system, buying the administration time and preserving outs should the president be persuaded to change course.

"This is not a 'buck stops here' president," said Douglas Brinkley, a presidential historian at Rice University. "His language is Trumanesque — unflinching and 'Here's what I'm going to do.' But it's just rhetoric. Once he tries to implement it as policy, he backs off. . . . He goes forward in a bully-boy fashion, but he gets his comeuppance."

[Trump plans to declare that Iran nuclear deal is not in the national interest]

Even if Trump's actions fall short of his rhetoric, they can have consequences. In the cases of the Paris climate accord and the Iran agreement, Trump's critics charge he is surrendering the United States' leadership role on important issues while potentially giving Washington less leverage in future negotiations.

Trump's advisers and allies reject the suggestion that his policy moves fail to live up to his promises. They argue that the president has purposefully articulated his policies in broad and declarative language, helping ensure his messages break through with the American people.

Furthermore, they note that Trump is hardly the first politician whose language has gotten ahead of his more complicated actions.

President Barack Obama signed an executive order on his first week in office to close the military prison at Guantanamo Bay, Cuba, promising to return the United States to the "moral high ground." But Obama's plan was never fulfilled, and the controversial detention facility remains open.

Obama also made sweeping declarations when he signed into law his signature health-care overhaul, such as promising that people could keep their doctors and that their premiums would not increase. But implementing the Affordable Care Act proved far messier than anticipated.

Obama has been a consistent theme in most of Trump's policies. That is, if a policy bears the Obama imprimatur, Trump's instinct has been to undo it — in part because his base demands he unravel or replace Obama-era policies.

For instance, Trump announced with considerable fanfare June 1 that he was withdrawing the United States from the Paris climate accord. Speaking from the Rose Garden of the White House, Trump declared the deal to be "very unfair, at the highest level, to the United States."

The takeaway from Trump's remarks was that the United States would be out of the accord immediately. But as with other issues, the reality is more complicated. The withdrawal mechanism takes more than three years to complete. In the meantime, the Trump administration is exploring ways to remain a part of the agreement by reducing U.S. commitments to cutting down carbon emissions, to levels the president believes would be fairer to U.S. industry.

"We're getting out," Trump said in his June 1 remarks. "But we will start to negotiate, and we will see if we can make a deal that's fair. And if we can, that's great. And if we can't, that's fine."

[Inside Trump’s climate decision: After fiery debate, he ‘stayed where he’s always been’]

Lanhee J. Chen, a Republican policy expert and fellow at Stanford University's Hoover Institution, said Trump has hit "a sweet spot" between communicating sweeping changes while actually taking more-incremental policy steps that preserve options.

"Most Americans are not particularly interested in the details and care to a certain degree, and Trump is figuring out what that degree is," Chen said. "It is a careful triangulation, but it's one that politically is going to be advantageous for him in the long run."

Chen pointed to Trump's handling of the nuclear threat posed by North Korea and its leader, Kim Jong Un, as another example of the gulf between the president's language and his administration's actions.

"Behind the scenes, there's a whole different set of activities going on," Chen said. "In public he's saying, 'Don't talk to Rocket Man — that's crazy.' But there clearly is an effort in the administration to open a dialogue."

The pattern is evident on other issues, as well. Trump has long boasted about building a wall along the U.S.-Mexico border — a signature campaign promise — but construction depends on Congress appropriating billions of dollars of public money to the project.

Addressing another campaign pledge, to tackle the growing opioid epidemic, Trump in August announced that he considered the crisis to be "a national emergency." His announcement generated headlines, but the administration has yet to take the legal steps officially declaring a national emergency.

On the Iran deal, Trump publicly has called the agreement reached in 2015 "the worst deal ever negotiated." But behind the scenes, he and his advisers have debated varying options ahead of Sunday's deadline for the government to certify whether Iran remains in compliance. The plan the president is expected to pursue would be more nuanced than a splashy termination.

Trump is expected to announce this week, probably Thursday, that he will "decertify" the deal and state that it is not in the national interest of the United States. This action alone would not derail the deal, however. Rather, it would fall to Congress to decide whether to reimpose sanctions against Iran, which would constitute a break from the pact.

People briefed on Trump's intentions previewed them to The Washington Post last week, although White House officials have cautioned that Trump's plans could change and that his decision is not final until he announces it.

"We're now stuck in this bad deal, and I think he's trying to respond measuredly," said Barry Bennett, a former Trump campaign adviser. "A lot of things require congressional approval, so when he does things like this that his base wants him to do and Congress sits on it for a while, it's why their approval rating is down."

To Trump's supporters, Brinkley posited, it may not matter whether Congress reimposes sanctions derailing the Iran deal. The word they will hear the president utter is "decertify."

"All his base knows is that he said Obama made the worst deal in history on Iran," Brinkley said. "Fewer people follow the minutiae of that deal. So he gets known to be the guy who dislikes Obama's deal, even though the deal may stick."