Americans stayed with President Obama on Tuesday, despite an economy that remains fragile. It was a hard-fought victory, but he has little time to savor the moment. The work must begin immediately, even if he is hobbled by the aftereffects of one of the most dismaying presidential campaigns in recent memory.

These races always offer a migraine’s worth of negative advertising, of course and, as former House Speaker Thomas P. “Tip” O’Neill famously observed, “Politics ain’t beanbag.” We expect these campaigns to be tough and aggressive.

Both Obama and Republican Mitt Romney strayed so far from the truth in this campaign that Americans couldn’t really know what policies they were endorsing with their votes. However, some facts are beyond dispute and they are critical to finding solutions. Here are some of the facts that Obama will need to deal with.

The most urgent piece of business Obama faces is the looming fiscal cliff that Congress created through its irresponsible refusal to deal with the federal deficit. Republicans demanded action on the deficit as a precursor to raising the federal debt limit and allowing the nation to pay its creditors.

But Republicans rebuffed Democratic proposals to cut spending and raise some taxes in a deal that would have caused everyone some pain, while dealing with an urgent issue. Instead, they agreed to the formation of a bipartisan “super committee” that would either agree on a deficit reduction plan or clear the way for $1.2 trillion in automatic budget cuts, with half coming from defense – at a time when Americans are at war.

Republicans and Democrats both agreed to this game of chicken, but the whole enterprise collapsed, leading to the imposition of those cuts come January – cuts that Defense Secretary Leon E.Panetta says would devastate the military.

That’s half the fiscal cliff. The other is the pending expiration of several tax cuts, including those that carry the name of President George W. Bush and the payroll tax cut that Obama crafted. The sudden expiration of all those tax cuts in a time of continuing economic weakness, together with draconian budget reductions, would bring on a new recession that would be disastrous.

It will be Obama’s job to thread that needle in the next two months. And what was necessary before is what is necessary now: an agreement that requires everyone to give in the service of a healthier federal balance sheet. If all Americans are not in this task together, its likelihood of success will be vastly diminished. Obama needs to take the lead in that urgent task starting tomorrow, and then he must continue – along a responsible path – to focus on deficit reduction for the remainder of his term. Trillion-dollar deficits may be tolerable during a severe recession, but they cannot become the long-term norm.

A large part of that will require the president and Congress, finally, to deal with the problems of Social Security and Medicare. Social Security is a comparatively easy fix, but Medicare will be more difficult. What is urgent is that the president and Congress protect it as a reliable health care partner for America’s seniors. With Obama’s victory, the threat that it would be mutated into a voucher program has been eliminated, at least for now.

On the international front, Iran’s quest for a nuclear weapon demands continued and even intensified attention. This is a hair-trigger issue that could set off a destructive region-wide war. That may happen – and sooner rather than later – but it is critical that Obama continue policies to avoid that war except as the last resort to prevent Iran from securing a nuclear weapon.

The Affordable Care Act needs to be revisited to do more to control the still-escalating costs of health insurance. The law has its merits, including the inability of insurers to deny coverage of pre-existing conditions and to dump subscribers when they get too sick, but it failed on the urgent matter of controlling costs. Without that component, health care will continue to fail.

As Obama found out in his first term, though, there is only so much a president can do without a Congress that meets the standards expected by the Founding Fathers: that its members will fight hard for their beliefs and their constituents, but retain the good sense to compromise to protect that nation’s well-being.

Congratulations, Mr. President.