As the crisis has deepened, Trump's language likening the outbreak to a war has grown more explicit. "We're at war, in a true sense we're at war, and we are fighting an invisible enemy," he declared in his opening statement at his press briefing Sunday. Trump's remarks even distantly echoed Abraham Lincoln's description of the Civil War as a "great fiery trial" when he declared: "We're enduring a great national trial and we will prove that we can meet the moment."

There's evidence in the latest polling that Trump, like other presidents at time of crisis, is benefiting from the traditional public instinct to "rally around the flag" at a moment of national unease. The invasion metaphor provides Trump both a sword and a shield: it simultaneously stokes the fear of foreign influence and immigrants that Trump has relied on throughout his political career, and seeks to recast criticism of him as unpatriotic when he is functioning in effect as commander in chief.

The critical question may be whether the public eventually blames Trump for what public health and medical professionals almost unanimously consider a catastrophic federal failure to take more decisive action at the outset -- or judge him primarily by his actions after his national emergency declaration earlier this month.

That announcement now looks like an explicit attempt to reset the clock on his performance just as more Americans themselves were becoming aware of the danger. If the public doesn't blame Trump for allowing the situation to become so dire in the first place, it may be more likely to credit him if America escapes the worst-case scenarios going forward.

One major uncertainty in this is how long Trump can stick with a message of wartime sacrifice and unity. On Monday, after days of soberly underscoring the threat from the virus, he whirled in a different direction, insisting at his daily press briefing that the country might face greater danger from a sustained economic shutdown than from loosening social distancing . For a purported wartime commander in chief, it amounted to declaring victory and pulling back the army long before the enemy -- in this case the virus -- has really surrendered.

Trump's virus rhetoric

For Trump, describing the pandemic as the "Chinese virus" or a "foreign virus," as he did in his Oval Office address earlier this month, serves several political aims at once, experts say.

One is to link the current outbreak with his larger effort to portray immigrants and foreign nations as a threat to the security and prosperity of his preponderantly white electoral coalition. Trump's effort to "weaponize the pandemic" by branding it as a foreign threat follows a long tradition of stereotyping immigrants as a source of disease, says Erika Lee, director of the University of Minnesota's Immigration History Research Center and author of the recent book, "America for Americans: A history of xenophobia in the United States."

Through American history, Lee says, it has been "really common" for American nativists to portray immigrants as a threat to public health. "Whether it be typhus and Irish immigrants and the bubonic plague and Chinese immigrants, cholera and Russian Jews, when Mexican immigrants were coming across the border after an outbreak of typhus in El Paso, they were literally sprayed with insecticide," she said.

Another factor: supporters and opponents agree that Trump always seems more confident politically when he has a clear foil to contrast with, and stamping the outbreak as the "Chinese virus" provides him one. Early on, both Trump and his cheerleaders in the conservative media mostly sought to point fingers at the mainstream press for allegedly exaggerating the threat. As the outbreak's spread has weakened that case, the attacks on China have increased in almost direct proportion.

Perhaps most important, likening the virus to a "foreign" invader locates the threat outside the country and helps Trump present himself as a wartime leader mobilizing the nation like Franklin Roosevelt after Pearl Harbor or George W. Bush after 9/11.

Positioning against Biden

The Trump campaign has already used that framing to accuse former Vice President Joe Biden of siding with the enemy. In a recent press release, Trump's campaign flatly declared, "America is under attack -- not just by an invisible virus, but by the Chinese," and then insisted Biden was on the wrong side of that fight. Biden, the Trump campaign argued in a release , is "siding with the Chinese and attacking the presidential candidate China fears most: Donald Trump."

Simultaneously the Trump campaign and other conservatives have argued that it is misguided, even unpatriotic, to second-guess or critique Trump's initial actions while the US is still fighting the threat. "I am so sick of seeking the news on Coronavirus and constantly getting bombarded w/how it's all Trump's fault or what Trump is calling the damn virus. Can we focus on what needs to be done right now and play the blame/political game later? Good Lord," the former Fox News host Megyn Kelly declared in a recent tweet

Democrats believe Trump's dilatory and distracted actions during the weeks when he repeatedly minimized (or dismissed entirely) the danger will ultimately swell doubts about his leadership, the way the faltering response to Hurricane Katrina in 2005 left a lasting stain on Bush's second term.

Trump "is now leaning into the notion of being a wartime president in part because somebody told him that war time presidents get reelected," says Democratic pollster Geoff Garin, who recently completed a national survey on public reactions to the crisis. "But my view on this is that the right analogy is that he's a disaster president and not a wartime president. From a political perspective this is much more like a national version of Katrina with the waters rising much higher and lasting much longer than it is like Pearl Harbor or 9/11."

Biden pointed to those potential vulnerabilities in the video he released Monday . "Trump keeps saying that he's a wartime president," Biden declared. "Well, start to act like one."

A false sense of security

Some public health experts say Trump's effort to portray the virus as a foreign threat may also expose him to the political risk of a wider and deeper outbreak. Such language, they say, can create a false sense of security that it can be blunted by walling off America from the outside world. And that could discourage more Americans from taking the threat seriously, at a time when polls show Republicans are already less likely to do so than Democrats . Describing the illness as a "Chinese virus," "supports the false narrative that disease can be contained elsewhere, along the same lines as travel bans," says Eric Toner, a senior scholar with the Johns Hopkins University Center for Health Security. "The disease is already here, it is already spreading person to person within the US. It's not a foreign disease anymore."

Democratic groups generally say Trump's efforts to build a wartime bunker around his actions won't deter them. Several outside groups, such as American Bridge and Priorities USA , have already launched television and digital ads focusing on the weeks Trump spent minimizing the threat, and failing to take aggressive action to begin testing or stockpile medical supplies. Josh Schwerin, a senior strategist at Priorities, the leading Democratic Super PAC, notes that Trump himself has hardly held to the principle that leaders shouldn't be criticized while they are coping with a crisis: Trump attacked Democratic Gov. Jay Inslee as "a snake" when Washington was the first state grappling with an outbreak. Trump remains quick to denounce on twitter any Democratic governor who criticizes his response to the crisis, such as J.B. Pritzker of Illinois.

In the early stages, the public response to Trump's handling the crisis is mostly flowing through the same deep grooves that have defined public reaction to almost everything else about his presidency, including his impeachment. Although the first round of media surveys found around 43% to 46% have given Trump positive grades for his handling of the crisis, those numbers rose in several internet polls last week. A Monmouth University survey released Monday found that exactly half of Americans gave Trump good mark for his response to the crisis, while his overall approval rating edged up to 46%.

Patrick Murray, the poll's director, noted in a release that "the small increase in [Trump's] current job rating falls far short of the 'rally round the flag' effect past presidents have experienced," during times of crisis, such as Bush after the 9/11 attacks. But any uptick for Trump may be surprising when set against the backdrop of the overwhelming outcry from public health professionals and medical personnel and governors in both parties that the federal government has suffered a series of catastrophic failures in developing and deploying tests for the disease, stockpiling personal protective equipment for caregivers and augmenting hospital capacity.

Even Democrats acknowledge the polling provides no evidence of a public verdict that Trump has failed so far in responding to the challenge. "I don't think there is a consensus about that," Garin acknowledged.

Partisan splits apply to coronavirus too

That judgment may reflect the durability of opinion about Trump, which has hardly ever oscillated outside of a narrow range through his presidency. But in another way, Trump may be standing on unsteady timbers. One key factor in public opinion is that Republicans in general, and Trump supporters in particular, remain less likely to view the outbreak as a serious threat to the nation or their community, or to report changing their personal behavior in response to it.

In last week's NPR/PBS NewsHour/Marist poll , fully 57% of Trump approvers said the risk of the virus was blown out of proportion compared to just 17% of those who disapprove of him. Likewise, the non-partisan Pew Research Center in a national survey released last week found that Americans divided almost exactly in half over whether they considered the virus a major threat. A solid majority of those who considered the coronavirus a minor threat or not a threat at all said they trusted Trump to handle the outbreak, according to detailed results provided by the pollster. But nearly half of Americans said they already considered the coronavirus a major threat and by a resounding margin of almost 2 to 1, they reported that they had little or no confidence in his ability to handle it. That suggests more voters might turn on Trump if the economic and health consequences of the outbreak persist.

That's certainly the dominant perspective among most Democrats, including senior strategists inside the Biden campaign. There the view is that no possible argument from Trump -- blaming China, blaming immigrants, or cloaking himself in the mantle of commander in chief -- will overcome the public's distress over outcomes that might not even approach the worst case scenarios. "You could easily see that we get through it but people are relieved, not triumphant, and don't ever want to go through that again so it becomes another thing that is as much a reason to get rid of the guy as it is to keep him," said one senior Biden adviser, who asked for anonymity to discuss the campaign's internal deliberations.

Gene Ulm, a Republican pollster, doesn't think Trump is doomed to rising discontent over his response. But he does believe Trump is hostage to events, and operating with limited time. Ulm anticipates the key to the political reaction will be how long American life remains heavily disrupted. "There is limited tolerance in time for this," he said. "And I think that the key function is time, where people want normalcy, they want a plan on a glide path to normal."

Ulm's framing underscores the gamble Trump has taken by encouraging Americans to see the virus as a foreign invader, and him as the resolute wartime leader repelling it. During wars, leaders often focus on steeling their countries for long and grueling struggles, the way Winston Churchill did by promising Great Britain only "blood, toil, tears and sweat" during the early stages of World War II.

Trump, with his marketer's instinct for boosterism, has taken instead to promising "a great victory... that, in my opinion, will happen much sooner than originally expected," as he put it at Sunday's briefing. Few, if any, public health officials, much less governors in the most heavily affected states, are that optimistic.

Trump will undoubtedly gain some political benefit if he's right and the virus' siege lifts faster and with less damage than most experts expect. But if America is still in the trenches against the coronavirus long months from now, Trump's promises of swift and certain victory may return to haunt him.