President Donald Trump's approval rating is up — a little bit.

In the RealClearPolitics average of all polls, it sits now at 47.3 percent, the highest mark since he took office.

There are a few ways to look at this. Certainly, it's a dramatically smaller boost than past presidents have gotten at the onset of crises. For that matter, it's far lower than the boost Gov. Andrew Cuomo has gotten in New York during this crisis.

Then again, Trump's approval rating just hasn't budged much at all during his presidency. Public opinion on him is deeply entrenched on both sides. So a simple jump of a few points to the high 40s is significant. It elevates Trump to a level at which he could very plausibly win re-election.

Beyond all of this, however, is the most important fact: We're only in the early stages of a pandemic without modern precedent. No one knows how this will unfold, let alone what effect it will ultimately have on how Americans view their president. We just have no idea what this story will look like when it's ultimately written.

But we do know how the stories turned out for other modern presidents who've faced sudden crises. There may not be any great coronavirus parallels in them, but here are three that might still be useful to keep in mind as the crisis unfolds:

1. Iran hostage crisis (1979-80)

Jimmy Carter was a deeply unpopular president when, on Nov. 4, 1979, Iranian revolutionaries seized the U.S. Embassy in Tehran and claimed 52 Americans as hostages, triggering what would become a 444-day saga.

At first, an outraged American public rallied behind its president. Just before the siege, Carter's approval rating had been a feeble 32 percent, and polls showed him in grave danger of losing his own party's nomination to Ted Kennedy.

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Almost overnight, however, Carter's approval soared to 54 percent, a level he hadn't reached in nearly two years. And he vaulted into a solid lead over Kennedy in the Democratic race.

Demonstrators perched atop the wall of the U.S. Embassy in Tehran, Iran, burned an American flag on Nov. 9, 1979. Bettmann Archive / Getty file

Carter tried to cement his newfound status by swearing off politicking and announcing that he'd remain in the White House — and away from all campaign activity — to deal with the crisis. For the next three months, his approval remained over 50 percent. It was in this time that Carter crushed Kennedy in the critical early wave of primary contests.

But as the hostage crisis lingered with no resolution (and a Carter-authorized rescue mission failed), Americans grew impatient. And the domestic complaints that had been undermining Carter before the embassy siege returned to the fore. By May, his approval was back under 40 percent for good. He did hold on to win the Democratic nomination and continued frantically trying to secure the hostages' release, but to no avail.

Deeply unpopular, Carter lost in a general election landslide to Ronald Reagan.

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2. The Gulf War (1991)

When Iraqi strongman Saddam Hussein's forces invaded Kuwait in the summer of 1990, President George H.W. Bush vowed that "this will not stand." Over the next months, he sent hundreds of thousands of American troops to Saudi Arabia and assembled an international alliance. Bush set a deadline of Jan. 15, 1991, for Hussein to relinquish his control over Kuwait — or face military action.

Public opinion was deeply divided. Vietnam was a fresh memory, and many feared another bloody quagmire. The Senate vote to authorize war was narrow, 52-47. Bush's domestic standing had been weakening, too, with a recession underway, and he'd recently broken his "Read my lips!" anti-tax pledge.

The deadline passed without Hussein budging and the war began, an aerial bombardment at first followed eventually by the launch of a ground war, which took just 100 hours. In total, the war claimed 146 U.S. troops, a vastly lower count than the dire forecasts Americans had absorbed in the run-up.

A destroyed Iraqi tank rests near a series of oil well fires in northern Kuwait on March 9, 1991, during the Gulf War. David Longstreath / AP file

With Iraq's quick surrender, all of that public anxiety transformed into a jubilant explosion of patriotic glee. Months of parades followed to welcome triumphant troops home. Even Bush's political adversaries hailed his wartime leadership. His approval rating climbed to an unheard-of 89 percent in the spring of 1991, and he was assumed to be a shoo-in for re-election the next year — so much so that every big-name Democratic leader opted to sit out the race.

And yet, there was still the matter of the recession. The revelry died down in the summer of 1991, and by the fall, Bush's approval rating was in the 50s. By the end of the year, it was under 50 percent. And by the summer of 1992, after five straight months of rising unemployment, it cratered at 29 percent. There were signs of economic life by Election Day, but it was too little, too late to save Bush, who finished with just 38 percent of the vote in a three-way race with Bill Clinton and Ross Perot.

3. 9/11

It had taken a 5-4 Supreme Court ruling to shut down a recount in Florida and seal George W. Bush's victory in the 2000 election, making Bush the first person in 112 years to become president despite losing the popular vote.

Eight months into his presidency, Bush's approval rating sat at 51 percent, and Democrats remained deeply resentful of the circumstances that had brought him to office.

And then, on the morning of Sept. 11, 2001, came the deadliest attack ever on American soil, with nearly 3,000 lives lost in about an hour. For days, a stunned and paralyzed nation remained still, processing its grief and bracing for what seemed like an inevitable follow-up attack. Americans looked to their president for guidance, and when Bush visited the devastation at Ground Zero in New York City, he seemed to lift the entire country's spirit with an impromptu pledge to seek vengeance.

Early morning light hits the smoke and wreckage of the World Trade Center in New York City on Sept. 13, 2001, two days after the terrorist attack. Chris Hondros / Getty Images file

Within a week, Bush's approval rating had jumped to 90 percent. He vowed a "war on terror" and soon authorized an invasion of Afghanistan to topple the Taliban and pursue Osama bin Laden. He embraced the role of wartime leader, and Americans embraced him. Bush's approval rating wouldn't fall below 60 percent for more than year, until early 2003, when his push for war with Iraq was coming to a head.

By 2004, as he sought re-election, Bush's approval rating was hovering around 50 percent, and the occupation of Iraq was proving to be far more difficult — and deadly — than he'd predicted. But memories of 9/11 remained raw, and anxiety about further attacks endured. Bush portrayed himself as unwaveringly focused on preventing another 9/11 from ever happening.

Despite strong concerns about the war, 51 percent of voters agreed to give him four more years.