Every now and again, President Trump chooses to embrace the office of the presidency, with all its pomp and power, if only to prove that he can.

The moments rarely last long, but they are notable when they arrive — at an international gathering in Switzerland, during a Medal of Honor ceremony or in an address to a joint session of Congress. 

Trump's first State of the Union address, Tuesday night, was designed to be one such moment. He offered a message of national unity and optimism, one that touched on the just-passed Republican tax plan, his new immigration proposal, and trade, infrastructure and national security. 

"No people on earth are so fearless, or daring, or determined as Americans," he said, playing rhetorical notes that president's have long employed in the speech. "If there is a mountain, we climb it. If there is a frontier, we cross it."

The question was whether the swirl of conflict and diversion that monopolized so much of his first year in office would distract from the message he was trying to deliver.

After a year as president, Trump has proved himself capable of reading words from a teleprompter. When he chooses, the former reality-TV star can summon a performance to rival that of Martin Sheen as the aspirational President Jed Bartlet on "The West Wing."

What is less clear, however, is whether he has the ability — or even the interest — to turn his well-delivered words into tangible results without self-sabotaging or undermining his and his team's best intentions. 

"There's no question that President Trump can deliver a speech," said Michael Steel, a Republican strategist. "The question is whether he has the discipline to turn his words into policies that help the American people — and when he'll set off another counterproductive Twitter firestorm about something like Russia, the NFL, or Bruno Mars at the Grammys."

Like the campaign that elected him, Trump's time in office has been built around the idea that what the nation needs now is a citizen-leader, not another politician, and that his primary role is one of disruption. 

 "It's so easy to act presidential, but that's not going to get it done," Trump said at a rally in Youngstown, Ohio, in July.

Yet one of the reasons Trump is able to credibly elevate both his rhetoric and the stature of his office on certain, scripted occasions is that he has a willing audience that is desperate to believe.

Congressional Republicans, for instance, are so worried privately about the impetuous leader of their party that they cling to any grain of normalcy — repeating it like a mantra to reassure themselves that Trump is, in fact, able to rise to the occasion of commander in chief. 

Many Trump supporters, too, say they wish he would not tweet as much as he does or would act more presidentially. And even many Democrats yearn for a return to normalcy of sorts, where a reported $130,000 payoff to a porn star who allegedly had an affair with Trump — a surefire scandal in any other administration — is not dismissed as a C-list sideshow. 

Much of the public appears to anticipate these fleeting moments in which Trump seems to understand and channel the gravity and import of the presidency, playing the role of a traditional leader. 

The problem, however, is that Trump so far has proved himself less a method actor than one able to briefly inhabit a role before slipping back into his more comfortable self. 

His policy positions are often only temporary notions, his calls for unity and bipartisan cooperation can be contradicted in the same day, and his ideological vision is often undermined by the laws that he ultimately signs. The facts he uses to defend his positions are also regularly proved to be false.

And none of this lends itself to the traditional role of the State of the Union, which voters, legislators and foreign governments look to as a guide to the nation's political agenda. 

But Trump embraced many of the tropes that have long defined the event. He repeatedly turned to the gallery to tell the stories of regular people he had invited to attend — law enforcement officials, workers who had benefited from his policies, the parents of crime victims, and even a 12-year-old who put flags on the graves of fallen members of the military.

He warned America's enemies of the nation's might, detailed the economic successes of the past year and ticked off a raft of future initiatives, including $1.5 trillion in infrastructure spending, a new training effort for prisoners and a goal of lowering prescription drug prices.

It was not the first time Trump demonstrated he can play the role when necessary. 

He delivered a similar address before a joint session of Congress last February. He began by praising Black History Month and denouncing threats against Jewish community centers. He painted a soaring vision of American renewal and economic optimism. And he laid out a series of carefully fact-checked arguments for his big policy pushes — for a tax overhaul, trade policy and infrastructure spending. 

"If we are guided by the well-being of American citizens, then I believe Republicans and Democrats can work together to achieve an outcome that has eluded our country for decades," he said at one point about his plans for immigration. 

Immediately after that address, in which Trump also honored the widow of a slain Navy SEAL — a moving moment that led to a sustained standing ovation — Van Jones, a liberal commentator on CNN, declared, "He became president of the United States in that moment, period."

Within days, Trump's unifying message was a distant memory. He accused former president Barack Obama, without evidence, of having Trump's "wires tapped" in Trump Tower during the 2016 campaign. The FBI's director later said there was said there was "no information" to support Trump's accusation. 

"The real problem is that people just do not listen to his words and treat them with the seriousness that they afford other presidents," said Michael Beschloss, a presidential historian. "He has been on so many sides of so many issues that even if it is a good speech, people will figure that it is not going to last long."

Republican leaders in Congress have nonetheless embraced the idea that Trump would stick to his broadly palatable script. Republican surveys in many key swing districts showed the president continues to poll below GOP incumbent members of Congress. 

That is not the only concern in a midterm election year, in which the fortunes of the president's party typically hinge on his popularity. In 2017 elections in Alabama, Virginia and the suburbs of New York City and Philadelphia, concern about the president's behavior proved to be a drag for Republican candidates by turning off suburban voters and driving Democratic turnout. 

Republicans are hopeful that Trump will stay focused over the coming months on selling GOP tax cuts as a boon to the middle class. "Success in the midterms hinges on selling the tax bill to the American people," said one senior Republican strategist. "To do that successfully, we need the president and the White House making the case every day instead of every sixth day." 

Tuesday night in front of Congress was a good place for Trump to start. In the pecking order of public presidential events, the State of the Union remains perhaps the most powerful platform, usually attracting between 30 million and 50 million television viewers, including a broad cross-section of Americans who do not follow day-to-day politics.

For nearly 90 minutes, Trump performed in the tradition of his office, praising the notion that he oversees a single nation with a single goal. "All of us, together, as one team, one people, and one American family, can do anything," he said.

Now the clock starts, testing how long he can stick with that message of unity.