WASHINGTON (THE WASHINGTON POST) - US President Donald Trump will deliver his first State of the Union address on Tuesday (Wednesday, 10am, Singapore time) at a juncture of opportunity and peril for his presidency, and his anxious allies hope he will show he has the ability to do something he has not done before: bring the country together.

White House officials have offered few details of what Mr Trump will say other than that he will take credit for a healthier economy and tie its continued growth to the Republicans' new tax plan, as well as argue his case on immigration, trade, infrastructure and national security.

In tone, they say, it will not be like the fiery populist inaugural address, in which Mr Trump offered a dark picture of "American carnage." A senior administration official who has been involved in the drafting promised "a speech that resonates with our American values and unites us with patriotism."

With its bumper-sticker-ready theme of "building a safe, strong and proud America," the address is expected to resemble the vision of a "renewal of the American spirit" that Mr Trump offered in his well-received speech to a joint session of Congress last February.

It also will come on the heels of the pragmatic, upbeat speech he delivered last Friday to a sceptical audience at the World Economic Forum in Davos, Switzerland.

The president has for months been making notes on points and phrases he thinks will resonate and sending those snippets to his staff, another aide said.

Yet it will be an incongruous picture the American public sees on Tuesday night: a divisive chief executive, who has discarded countless norms, performing one of the most traditional of presidential rituals - an hour or so during which, uninterrupted and unfiltered, he can claim ownership for his accomplishments and set an agenda for the year ahead.

Democrats, meanwhile, have chosen Representative Joe Kennedy, a Democrat from Massachusetts, a charismatic new political star who has a universally known family name, to give their official response.

The larger question is whether Mr Trump can expand his appeal beyond his ardent base to reach the majority of Americans who are responsible for his historically poor job-approval ratings.

"Coming off the tax cuts and the trip to Switzerland, he's in a position to be very presidential, and my hope is he will speak as the leader of the country and would offer a series of proposals that would bring us together," said former House speaker Newt Gingrich, a Trump adviser and defender.

"I don't think this year he needs to speak to part of America. He needs to speak as president."

Republican Judd Gregg, a former New Hampshire governor and US senator, counseled that Mr Trump should tamp down his tendencies to personalise every issue and instead look outward: "Optimism is the key word - optimism that isn't self-congratulatory, hopefully."

The stakes for his party are high as Republicans approach an election season with Democrats increasingly bullish about their prospects of winning back one or both houses of Congress. That would break the Republican lock on power in Washington, thwart the president's ability to enact his agenda and imperil a second Trump term.

Regardless of whether Mr Trump mentions it, an unseen presence looming in the House chamber will be special counsel Robert Mueller III's probe into Russian meddling in the 2016 election. The inquiry appears to have reached a critical phase, with the possibility that the president himself may soon be interviewed by investigators.

Such a situation is not without precedent, and presidents have handled it in different ways. In his 1974 State of the Union speech, President Richard Nixon made what would turn out to be a futile effort to staunch the scandal that was engulfing his presidency by addressing it directly.

"I believe the time has come to bring that investigation and the other investigations of this matter to an end," Nixon said. "One year of Watergate is enough."

Ex-president Bill Clinton made his 1998 address less than a week after most of the nation heard the name Monica Lewinsky for the first time. Speculation was high that his resignation might be imminent.

The day before the speech, frantic aides scheduled a public appearance at which reporters would have an opportunity to question him, in the hopes that it would relieve some of the pressure. It was at that event that Clinton memorably - and disastrously - insisted: "I did not have sexual relations with that woman, Miss Lewinsky."

A year later, Mr Clinton delivered his State of the Union speech in the House chamber while his impeachment trial was underway in the Senate. However, he kept his focus on the "longest peacetime economic expansion in our history" and on his plan to protect Social Security.

"The most capable White Houses leverage this moment to not just be a night of television where you have a big national audience, but to set both the message and policy agenda for the year," said Ms Jennifer Palmieri, who was a White House aide in the administrations of Clinton and President Barack Obama. "It should be an effective organising tool for your whole administration. But I do not believe that this White House is capable of leveraging the State of the Union in that way, because there is no governing theory."

White House aides, however, say the president will have plenty to say on policy.

Mr Trump will try to find bipartisan support for the immigration framework he has laid out, which includes expanded protection and a path to citizenship for young undocumented immigrants brought to this country as children in exchange for US$25 billion (S$33 billion) for his border wall and more restrictions on legal immigration.

In the national security section of the speech, he is expected to address the ongoing nuclear threat from North Korea. Aides said he also plans to reiterate the international economic message he took to Davos: that the United States is open for business.

There will be touches that the national audience has come to expect in a State of the Union address. The White House has chosen a set of everyday Americans to sit with the first lady and have a moment in the spotlight as Mr Trump tells their stories. Among them: someone who will be portrayed as a beneficiary of Republican economic policies, and someone who has been affected by the opioid crisis.

Even if the State of the Union address lives up to the White House's billing, there remains the possibility that Mr Trump will do what he has done in the past: step on his own message.

Just days after his carefully crafted address to the joint session last February, for example, Mr Trump detonated a string of tweets accusing Mr Obama of having wiretapped Trump Tower, declaring, "This is McCarthyism!"

Instantly, that unsubstantiated charge overshadowed the speech. "A year later, people have a skepticism about him in these moments," said Mr Michael Waldman, a chief speechwriter for Clinton and now president of the Brennan Center for Justice at New York University School of Law. "Everybody knows that teleprompter Trump can come close to sounding like a normal president, and Twitter Trump will upend that."

Nonetheless, the White House has plans for Mr Trump and his Cabinet to travel in the days after the speech to amplify and promote the agenda he lays out."This is the time when you're master of your message and you're in charge," said Mr Ken Khachigian, who was a top speechwriter in Ronald Reagan's White House. "Take three or four or five days and bask in the glory."