Washington (CNN) President Donald Trump will face one huge obstacle when he appeals to Americans in a prime-time Oval Office address Tuesday to unite behind his crusade for a border wall: Himself.

Trump has spent years exploiting immigration -- one of the nation's most divisive fault lines -- during an insurgent campaign and a presidency sustained by the fervor of his committed political base.

But now, the downside of that strategy is becoming evident. In his attempt to convince the nation that a genuine crisis is unfolding at the southern border , the President's arguments face extreme skepticism from those not already in his camp.

About 57% of Americans oppose Trump's wall compared with 38% in favor, according to a December CNN poll conducted by SSRS . Those numbers are similar to where they were just after Trump took office in 2017.

On Tuesday night, Trump will commandeer the symbolic might of his office in an effort to bolster a political approach that has failed to force Democrats to cave to his demand for $5 billion in wall funding amid a government shutdown now in its third week.

He will hold forth on a deeply contentious issue from the spot where President Ronald Reagan eulogized the Challenger space shuttle crew and where other predecessors gave notice of the start or ends of wars.

The historically resonant stagecraft represents an attempt to convince the country -- with scant hard evidence -- that a real threat is unfolding on the frontier of the US and Mexico border, including drug trafficking, rising sickness among migrants, increasing border crossings and a busted asylum system.

"The American people will hear from the President tonight that we have a crisis," Vice President Mike Pence told "CBS This Morning" Tuesday, part of a series of appearances on network morning shows to make the administration's case. He urged Democrats to "come to the table" to make a deal but did not indicate that the administration's funding demand was negotiable.

Trump's capacity to make a similar argument is complicated by his choice not to broaden his support beyond his loyalist base in two years in office. And he's often used immigration as a cudgel to attack Democrats and moderate Republicans.

The address promises to be yet another extraordinary moment in a singular presidency. When news broke of his prime-time appearance, a remarkable debate broke out in Washington about whether the President of the United States can be trusted to tell the truth in an address to the nation.

Democratic House Speaker Nancy Pelosi and Senate Minority leader Chuck Schumer demanded the right of reply.

"Now that the television networks have decided to air the President's address, which if his past statements are any indication will be full of malice and misinformation, Democrats must immediately be given equal airtime," they said in a joint press release.

Pelosi and Schumer will deliver the response for the Democrats, which CNN will carry live.

'Build the wall'

Many Trump supporters do believe that the border is being besieged by criminals, is easily penetrated by drugs and gangs, and share his view that "without borders, we don't have a country."

And the President can clearly argue that he won election by promising to purge deep concern about a broken immigration system. At almost every rally, Trump beams as the crowd chants "build the wall, build the wall." The border issue has become an almost mystical symbol of Trump's appeal to his supporters.

But Trump has also stigmatized Mexicans and other immigrants and his dark vision of a nation under siege from hordes of invaders has turned a border security dispute into a political quarrel that tears at American cultural and racial divides.

The wall is just as powerful a metaphor for liberals, including Democratic leaders he now wants to fund the project after failing to get it built during two years of GOP control on Capitol Hill.

For Trump's critics, the wall is a metaphor for an inhumane and un-American approach to immigration that has seen undocumented migrant families separated and several detained children die of illnesses.

So, when the President seeks to corral public opinion behind him Tuesday, he will be operating on scorched political ground and will require something extraordinary to shift opinion.

That is especially the case since Trump's hardline rhetoric on immigration was seen by critics inside and outside of the GOP as a key factor in the party's loss of the House in the midterm elections.

The risk for Trump is that after the fire and fury of his relentless immigration rhetoric, anyone left who has an open mind simply will not believe him.

"I expect the President to lie to the American people," said New York Rep. Jerrold Nadler, the Democratic chairman of the House Judiciary Committee on Monday.

"Why do I expect this? Because he's been lying to the American people and his spokespeople continue lying to the American people," he said.

In the latest notorious case of the administration peddling untruths, White House spokeswoman Sarah Sanders was caught on Fox News implying falsely that up to 4,000 terrorists have poured over the southern border.

In an annual terrorism report published in July 2017, the State Department reported that there was "no credible information that any member of a terrorist group has traveled through Mexico to gain access to the United States."

White House counselor Kellyanne Conway told Fox News Monday night that Sanders got "confused" and made an "unfortunate misstatement."

"So, I think, it got unfortunately confused by my colleague," she said. "That was an unfortunate misstatement and everybody makes mistakes."

Conway said the nearly 4,000 people Sanders was referring to are known or suspected terrorists prevented from entering or traveling to the US via any means - not just over the southern border.

'Immigration arguments not landing'

Trump has claimed that a wall is needed to deter "drug dealers, human traffickers and criminals."

He also argued without evidence that a caravan of migrants from Central America that headed to the border last year included "unknown Middle Easterners" -- another reference to terrorism.

Such a record will complicate Trump's attempts and those of his key aides, such as Pence and Homeland Security Secretary Kirstjen Nielsen, who are due on Capitol Hill Tuesday to sell his message before the President heads to the border on Thursday.

CNN's Kevin Liptak reported on Monday that Trump's decision to deliver a prime-time address followed warnings from advisers that his arguments about immigration -- delivered in tweets and impromptu media scrums in recent days -- are not resonating amid the shutdown.

But if Tuesday's speech is pockmarked with factual errors and easily discredited spin, any hope the President has of influencing anyone other than his supporters will likely be dashed.

The President's set piece speeches have rarely succeeded in changing public opinion on a key issue or easing tensions in a political standoff; in fact, the opposite is more often the case.

Trump's decision to trigger a shutdown, apparently fearing anger from conservative pundits if he folded over wall funding, left an impression that he is covering up his embarrassment over his so-far failed campaign promise.

Given his hyper political approach in the past, it's always possible that Trump has no expectation of changing the partisan brew over immigration, but just wants to show his supporters he's ready to fight.

Trump's most difficult assignment will be to make a case that the situation at the US-Mexico border really amounts to a genuine crisis.

Apprehensions of undocumented migrants coming across the border did rise by about 100,000 in the 2018 fiscal year to nearly 400,000. The administration has also warned of a rise in families crossing the border illegally. The numbers reached more than 51,000 families in October and November. But the figures are still nowhere near record-setting levels of up to 100,000 families a month in the early 2000s.

Nielsen told reporters at the White House that the asylum system, which was designed to process far fewer applications was "bogged down."

But the White House's critics are more likely to put those failures down to the administration's draconian approach and mismanagement than to an outside crisis that truly threatens US national security.

CNN's Tammy Kupperman, Geneva Sands, Jim Acosta and Betsy Klein contributed to this report.