Washington (CNN) President Donald Trump embarks on his debut State of the Union address Tuesday with the formidable assignment of shoring up a presidency threatened by a Russia scandal that is sowing rancor in Washington and tearing at national unity.

If the pattern of Trump's presidency up to now holds, his political base will give his speech an enthusiastic welcome and regard any criticism of the President as the typical response of biased mainstream media. But saddled with approval ratings below 40%, it's a fact that the President's capacity to win over the rest of the nation is compromised.

Whatever he says is also likely to be in part overshadowed by signs the Russia investigation is reaching a critical point, amid intense attempts by Republicans to discredit special counsel Robert Mueller's team. The same could be said about bitterness smothering Washington after the recent government shutdown and resentment stirred by an immigration debate that is an existential issue for both parties, and could yet shut the government again early next month.

Presidents typically use the annual showpiece to invoke national togetherness, to reach across partisan divides and to market political priorities while relishing the pageantry of an occasion designed to highlight their power and prestige.

Yet because of the way Trump has acted as President -- pulling at societal and cultural divides and rarely attempting to reach out beyond his political base -- his capacity to reshape the political environment Tuesday may be limited.

Trump's propensity to trample on his own scripted political moments and his use of Twitter to vent his own anger and spark outrage has hardened attitudes about him among the public. It may even ultimately diminish the transforming potential of Tuesday night's big speech.

Unfiltered

Still, the State of the Union address remains the one moment in the year when the President, assured of a massive television audience, can hold court unfiltered and unchallenged while basking in the kinds of standing ovations that feed Trump's hunger for affirmation.

The White House says Trump will use Tuesday night's address to assert that his cuts in taxes and regulation have unleashed a new era of economic prosperity as he seeks to garner credit for achievements he believes have not yet won sufficient recognition.

He will maintain that he is rebuilding the US military and restoring an American posture of "peace through strength" in the world. Trump will also take the chance to sell his plan to shield from deportation undocumented immigrants brought to the US as children in return for massive funding for his border wall, a proposal that Democrats have already rejected. The President is also expected to push his infrastructure plan -- one initiative that might win some Democratic support.

White House spokeswoman Sarah Sanders promised that Trump's speech, which he practiced in a full run-through on Monday, would be "incredible."

"We've got an economy that is booming. ISIS is on the run. We're remaking the judiciary in a way that actually believes in upholding the Constitution. There are some great things happening in this country," Sanders said Monday.

In some ways Tuesday's speech will mark a moment of transition for the Trump presidency. Up to now, Trump has done little to try to convince voters who disdain him that he is their President, too. But arguing to the nation that its economic prospects have soared under his leadership is an implicit plea to those who dislike him to overlook their reservations for their own financial well-being. It's an argument that is likely to form the basis for Republican efforts to cling to House and Senate control in the midterm elections in November.

But given how political divides have hardened over Trump's presidency, it's questionable whether there are many Americans who have yet to make up their mind about him.

"Now the country is so divided with people on the hard right and people on the left who have reacted to President Trump, I think there's going to be very few people in the middle who will actually listen to this," said Ohio's Republican Gov. John Kasich on CNN's "New Day" on Tuesday.

Measuring stick

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Trump's address will draw immediate comparisons with his speech to a joint session of Congress a month into his presidency last February -- and may not be flattered by the comparison. On that occasion, Trump won good reviews for his demeanor and unexpectedly statesmanlike approach, and appeared to cut a more conventionally "presidential" figure than he has at any time since.

The highlight of the night came when Trump directly addressed the widow of fallen Navy SEAL William "Ryan" Owens , who was seated in the first lady's box in the House of Representatives.

In February, it was still credible to ask whether the speech represented a turning point that the President was using to signal a change of approach and a more inclusive style of governing.

One year in, however, after divisive controversies like Trump's equivocal response to racially motivated protests in Charlottesville, Virginia, and his assault on legal and judicial institutions amid the Russia probe, it would be more difficult to make a similar case for Tuesday's appearance.

Aaron Kall, editor of a new book, "The State of the Union Is ...," looking at how different presidents approached the annual speech, says Trump had a much more complicated assignment Tuesday than he did in February, especially given his record of torpedoing his own successes.

"There have been some great State of the Union addresses -- Bill Clinton and Ronald Reagan -- but they didn't have Twitter and the opportunities for them to sabotage their public performances did not exist in the same way," said Kall, director of debate at the University of Michigan.

The bar for Trump's first joint address to Congress a year ago was low, Kall said, because of the polarizing "American carnage" rhetoric of his inaugural address . By contrast, his more conciliatory performance in the House of Representatives came as a surprise. But the boost did not last.

"Just a few days later, he gets onto Twitter and starts with the conspiracy of President Obama wiretapping Trump Tower and then all the goodwill from that was erased," Kall said of Trump's unfounded claim.

Political survival in question

Trump will not be the first president to give a State of the Union address as scandal swirls around his administration, potentially putting his political survival in question.

In 1974, Richard Nixon traveled up to Capitol Hill with the Watergate scandal closing in. He decided to address it directly in his speech in a move that backfired and could not stave off his eventual demise later in the year.

In 1999, President Bill Clinton delivered his address after being impeached by the House of Representatives and amid his trial in the Senate.

Unlike Nixon, the Democrat did not mention his own political fate, choosing instead to anchor his remarks in the wider context of his campaign to convince the American people that he was working hard on their behalf.

Clinton stressed budget surpluses, rising wages and homeownership, thinning welfare rolls and falling violent crime, implicitly making an argument that the country would be foolish to throw him out of office.

In an essay in the book edited by Kall, Eric Morris, associate professor of communication and director of forensics at Missouri State University, suggests that Trump would be well advised to follow Clinton's example and speak about anything -- except the investigation against him.

"Just as Clinton's silence regarding his impeachment and trial was an effective way of elevating the presidential role above perceived self-interest, silence about the Russia investigation might serve President Trump well," Morris wrote.

A senior White House official told CNN's Jeff Zeleny on Monday that despite his frustrations with the Russia investigation, the issue was not included in the President's State of the Union script.

"That's not the point of the night," another senior administration official said.

But of course, Trump's entire presidency is based on straying from the script -- so no one can guarantee that he won't take matters into his own hands, with unpredictable political results.