Congratulations, Mr. President. You’ve overcome one of the nastiest political campaigns in the nation’s history. And, at $2.6 billion, one of the most expensive. You won.

Now, a dose of reality.

In 55 days, the nation faces a fiscal challenge unlike any other — a crisis entirely of our leaders’ own making and one that, unfortunately, was barely discussed in the small-bore campaign that ended with Barack Obama’s re-election Tuesday night.

On Dec. 31, the Bush-era tax cuts expire and billions of dollars of automatic spending cuts take effect. We will have reached the edge of the “fiscal cliff.”

The country’s finances are near this precipice because Obama and Republicans in Congress couldn’t agree on a deal to put them on a solid foundation last year. Instead, they squabbled, played politics, blamed one another and then loaded a gun and pointed it at themselves.

Here’s what should happen now:

Mr. Obama, you should lead.

You should embrace the spirit of the National Commission on Fiscal Responsibility and Reform — the commission you appointed — which called for a combination of spending cuts, tax reform, changes to entitlements and increased federal revenue over a period of years to put the federal budget on a more sustainable path.

If Congress does nothing, the U.S. economy would be plunged into anther recession, the Federal Reserve and the Congressional Budget Office agree. The direct hit to the economy of higher taxes and large spending cuts all at once would be that harmful.

Larry Fink, chief executive at Black Rock, a financial services company, put it this way in an interview with the Financial Times:

“Every day we go without a resolution to the fiscal cliff will erode confidence,” he said. American companies have $1.7 trillion in cash, “a huge reservoir of money standing by to be put back into the economy” if there was a fix that is seen as “tangible and credible.”

Groups of lawmakers in both the House and Senate have been meeting privately, hoping to sketch out the contours of what a “tangible and credible” deal might look like. But don’t expect anything that ambitious to emerge from the lame duck session that will begin soon after the election. There simply isn’t enough time or, apparently, enough will.

House Speaker John Boehner, R-Ohio, told Politico recently, “I think that’s difficult to do, and frankly, I’m not sure it’s the right thing to do — have a lot of retiring members and defeated members voting on really big bills.”

Diane Lim Rogers, an economist at the Concord Coalition, a nonpartisan organization that focuses on fiscal issues, says the most likely outcome is an extension that sets the stage for a serious debate over taxes, spending and entitlement programs in 2013.

“The most likely outcome is that we don’t go over the cliff when we are scheduled to go over the cliff,” she told us in an interview on our weekly video segment, “Fourth & State.” “I think the hope would be that we don’t kick the can very far down the road. And at the same, as we’re kicking the can, we set up a better process to make sure we don’t make the same excuses the next time the can lands.”

Like us, Rogers is concerned that Republicans are setting the revenue bar too low. They want to hold the line at 18 percent of national output (Gross Domestic Product), which has been the historic average for the past 40 years. Federal spending over the same time has been about 21 percent. In most of those years, the economy grew fast enough to make up the difference — or at least much of it.

But times are different now. Economic growth is slower and might remain slow for a while. At the same time, the baby boomers are beginning to retire in larger numbers, drawing Social Security and tapping Medicare funds. Federal revenue will have to be higher than the historic norm to meet those obligations.

Through tax reform that flattens rates and closes loopholes, the government ought to be able to raise more revenue. Even as the economy picks up steam, tax reform that additional revenue will be needed. Tax reform also should aim to simplify an often Byzantine system.

Spending, meantime, should be trimmed — but not abruptly. In fact, none of this should be done abruptly, despite the angry calls for pounds of flesh demanded by the tea party right, which was dealt a blow with the defeat of two extremist U.S. Senate candidates Tuesday night.

The main point: The federal government needs to put in place a long-term, sustainable plan to reduce deficits. But it has to be realistic — and it shouldn’t cut too deep, too fast at the risk of the economy. Social Security, Medicare and Medicaid need reform to make them more efficient and to ensure that they last. As currently constituted, they cannot last. Democrats need to accept this fundamental fact and work for meaningful and fair reform.

All of this requires leadership — leadership that so far has been absent.

So how about it, Mr. President? Now is the time.

The above editorial appeared in the Milwaukee Journal Sentinel on Wednesday, Nov. 7