WASHINGTON — President Trump leaves little doubt about what he thinks of his predecessor’s top domestic and international legacies. The health care program enacted by President Barack Obama is “outrageous” and “absolutely destroying everything in its wake.” The nuclear deal with Iran is “one of the worst and most one-sided transactions the United States has ever entered into.”

Yet as much as he has set his sights on them, Mr. Trump after nearly nine months in office has not actually gotten rid of either. Instead, in the past few days, he took partial steps to undercut both initiatives and then left it to Congress to figure out what to do next. Whether either will ultimately survive in some form has become a central suspense of Mr. Trump’s first year in office.

In the case of health care, Mr. Trump is making a virtue of necessity. Having failed to push through legislation replacing the Affordable Care Act, he is taking more limited measures on his own authority aimed at chipping away at the law. On the other hand, when it comes to the Iran deal, he has the authority to walk away without anyone else’s consent but has been talked out of going that far by his national security team. Instead, by refusing to recertify the deal, he rhetorically disavows the pact without directly pulling out.

These are not the only instances in which Mr. Trump’s expansive language has not been matched by his actions during this opening phase of his presidency. On immigration, diplomatic relations with Cuba and international accords like the North American Free Trade Agreement and a separate trade pact with South Korea, he has denounced decisions made by Mr. Obama or other previous presidents without fully reversing them.