Barack Obama marks his first 100 days as US president on Wednesday with swine flu freshly embossed on a long list of domestic and foreign crises to trouble his nascent administration, but with a measure of good news from Congress.
Up against the deepest recession since the Great Depression of the 1930s, wars in Iraq and Afghanistan and a controversial program of economic reform, Obama must also work to prevent a global pandemic.
The White House initially expressed its reluctance to take part in the media frenzy surrounding the traditional 100-day performance milestone, dismissing it as a "Hallmark holiday," but has since decided to play along.
Marking the occasion, Obama travels on Wednesday morning to St Louis in the Midwest state of Missouri for a town hall meeting to take the pulse of the nation's breadbasket, where the economic crisis has hit hard.
He then returns to Washington for a press conference where he is expected to give his own assessment of his early performance.
Obama's own spokesman Robert Gibbs gave his boss a report card grade of "B plus," noting "there's always room for improvement."
"I think the president and the administration are pleased with what has been done in the first 100 days if you look at restarting credit flowing, increased financial stability, (and) the passage of a recovery and reinvestment plan," he said Monday.
Obama has tried to steady the country's nerves despite a wrenching economic crisis.
The president unleashed a huge government intervention in the economy, passed a historic 787-billion-dollar stimulus bill and now has high-stakes environmental and healthcare reforms on the launchpad.
Abroad, Obama dumped George W Bush's swagger for a more humble tone, reaching out to Muslims and vowing to end decades of enmity with foes Cuba and Iran.
He previewed fundamental shifts in policy towards China, Mexico and Cuba, apologized to Europeans for past US "arrogance," mandated the closure of Guantanamo Bay, outlawed torture and ordered withdrawal from Iraq.
He also doubled down in Afghanistan and Pakistan, reversed US denial on climate change and called for a world free of nuclear weapons.
"It is clearly the most ambitious agenda at least since the 1960s," said Princeton University historian and political scientist Julian Zelizer.
But many of the new policies have not sat well with Republicans, who for the first time in eight years control neither the White House nor either chamber of Congress.
"We don't have a majority. It's very difficult to pass legislation," Republican Senate Minority Leader Mitch McConnell told reporters who asked him to grade the party's performance since Obama's January 20 inauguration.
Compounding their woes, senior Republican Senator Arlen Specter announced on Tuesday that he was becoming a Democrat, boosting Obama's ability to drive his audacious agenda through the US Congress.
The decision will give Obama's Democratic allies the 60 Senate votes needed to thwart Republican delaying tactics, provided Democrat Al Franken wins the long-delayed Minnesota Senate race.
Meanwhile Obama faced the first US health crisis of his administration, with the country bracing for its first swine flu deaths and officials nervous of an accelerating outbreak after the disease's emergence in Mexico.
At least 65 infections were confirmed in the United States, and after declaring a public health emergency at the weekend Obama pressed Congress to release $1.5 billion in emergency funding.
The White House is looking past Obama's whirlwind early performance and expects Americans will do the same.
"I think the American people are less likely to spend a lot of time sitting around Wednesday judging what we've done in our first 100 days, and are more concerned with what we're going to do each and every day going forward," Gibbs said.
In a national CNN/Opinion Research Corp conducted days before the milestone, Americans expressed their confidence in Obama as he navigates the crises before him.
Sixty-three percent of respondents said they approve of how Obama is handling his job as president, but just 28 per cent of opposition Republicans said so, according to the poll released on Monday.