Thomas E. Mann, a senior fellow at the Brookings Institution, and Norman J. Ornstein, a resident scholar at the American Enterprise Institute, are the authors of “It’s Even Worse Than It Looks: How the American Constitutional System Collided With the New Politics of Extremism,” which comes out as an expanded paperback Tuesday.

A little more than a year ago, we published a book about American politics — and particularly Congress — titled “It’s Even Worse Than It Looks.” In our book and in these pages, we lamented the ideological divides in Washington, which had become almost tribal in nature, and the skewed nature of political polarization, emphasizing a Republican Party gone off the rails.

Unfortunately, little has happened in the time since to lift our spirits. But we can always fantasize, right? For a moment, we want to rise above the pessimism about politics that permeates the capital and the nation and imagine a best-case scenario for what might happen when Congress returns from its August recess.

The challenges are daunting: economic growth too slow to counter high unemployment and stagnant wages, inadequate investment in job training and infrastructure that could boost prospects for the working and middle classes, and long-term fiscal imbalances flowing from an aging society and rising health-care costs.

And then there are the self-inflicted wounds: A federal sequester that is wreaking havoc on public goods such as scientific research, the administration of justice and preschool education. An inability to agree on spending targets for the budget year beginning in a month, threatening a government shutdown at worst and underfunded “continuing resolutions” at best. And more debt-ceiling brinkmanship that destabilizes the U.S. and global economy.

Clockwise, from top left: Republican Sens. Richard Burr (N.C.), Bob Corker (Tenn.), Tom Cole (Okla.) and John McCain (Ariz.) have spoken out against shutting down the government over Obamacare. (AP)

Our fantasy begins with the handful of Republican lawmakers who are speaking openly about the folly of pursuing blackmail. Sen. Richard Burr (N.C.) won the bluntness award when he labeled his colleagues’ proposal to shut down the government unless Obamacare funding is eliminated as “the dumbest idea I’ve ever heard.” Other Republicans in the Senate, including John McCain of Arizona and Bob Corker of Tennessee, have begun to chafe under the strictures of their party and have been joined by respected House Republicans such as Tom Cole of Oklahoma.

Now imagine if some influential outsiders joined them. What if the U.S. Chamber of Commerce lobbied lawmakers to stop their threats and pushed them toward an agenda for economic growth? What if the resources and energy of the Campaign to Fix the Debt, an elite business group spearheaded by the Committee for a Responsible Federal Budget, were dedicated to mobilizing public opinion behind a platform of “First do no harm: No sequester, no government shutdown, no debt-ceiling hostage-taking”? That could do more than years of ineffectual calls for bipartisan grand compromises and tax reform.

The legislative action would start in the Senate, where a bipartisan group would craft an omnibus package to fund the government and replace the sequester — all nine remaining years of it — with reasonable caps on defense and domestic discretionary spending. The rest of the budget savings from the sequester would instead come from modest, means-tested changes in Medicare and Social Security benefits, expansion and strengthening of some of the cost-control measures in the Affordable Care Act, and tax increases and fees to finance the costs of our aging society.

The package would also take the debt limit off the table by raising it at least until the end of Obama’s term or by institutionalizing the “McConnell rule” — allowing the president to increase the debt limit unilaterally and requiring a two-thirds majority in both houses of Congress to countermand him. And it would create a national infrastructure bank to leverage private investment in rebuilding our public transportation, sewer, water and energy systems.

A package that acknowledged progress already made on the deficit and aimed first to do no harm, incorporating ideas from both sides and some measures that are anathema to each side, would garner broad support in the Senate, perhaps 75 votes. It would be applauded by business and labor leaders and received enthusiastically in the markets, putting pressure on Speaker John Boehner (R-Ohio) to bring the measure to the House floor, with or without the support of a majority of Republicans. It would probably pass the House with the support of at least 190 Democrats and 30 or more Republicans.

The enactment of such a measure, focusing on the problems we face rather than serving a radical ideology, would do wonders to boost the economy and restore some public confidence in Congress. It might even set the stage for the completion of immigration reform.

The elements of this package are neither fanciful nor radical, but fit within the broad center of the American policy debate. One could easily imagine Ronald Reagan or Bill Clinton embracing them all. And our fantasy is based on a real understanding of today’s political hurdles, including that most House Republicans would oppose such legislation or any comparable alternative, and that even a broad bipartisan Senate coalition would mean about half or more of that chamber’s Republicans voting no.

But now, the fantasy turns back into a pumpkin.

The chances of such a deal materializing are slim to nonexistent. Some of the reasons became especially obvious this August. House Republicans around the country encountered angry constituents — goaded by GOP Sens. Ted Cruz of Texas and Mike Lee of Utah — demanding that they hold to the threat to shut down the government unless Obama agrees to defund Obamacare. Heritage Action, the political arm of the Heritage Foundation, just announced a $550,000 online petition campaign threatening mayhem against 100 or more House Republicans if they don’t agree. A number of House and Senate Republicans have openly mused about impeaching the president, adding to the difficulty of crafting any deal that Obama would support.

If more-reflective Republicans such as Cole see this as folly, the way Boehner has fended off his radicals is to suggest a better way to hit Obamacare and slash spending even further: using the debt limit again for leverage. But that means any effort by Boehner to embrace or legitimize a plan that doesn’t defund Obamacare in its effort to avoid catastrophe on America’s full faith and credit would be roundly condemned by a large core of his party members, not to mention Rush Limbaugh and Jim DeMint, weakening him further.

Of course, all of this reflects the fact that the House Republican majority is not being run by its leaders but by its most extreme faction, its role amplified by outside media and money. Among those who are less driven by rigid ideology, the threat of a well-financed primary challenge sharply deflates the number of those eligible for Profile in Courage awards — or willing to risk their congressional careers to get them.

The Senate is better but not a model itself. The ruthlessly pragmatic minority leader, Mitch McConnell (R-Ky.), is in full crisis mode, facing a primary challenge from the right that is forcing him to play nice with Cruz and fellow Kentucky Sen. Rand Paul and not cut more deals. The No. 2 Republican leader, John Cornyn (Tex.), has his own campaign headaches. And we saw the challenge to bipartisan action up close as a modest gun background-check bill failed to garner 60 votes because, as Sen. Pat Toomey (Pa.), its Republican sponsor, told reporters, too many of his colleagues would not vote for anything supported by the president.

We want to be optimistic, we really do. Our fantasy would have had some chance in the reality of the 1970s, 1980s or 1990s — all eras with plenty of dysfunction and partisan polarization. Even today, we could name 75 senators who, under the right circumstances, would support the kind of package we outline. But the rampant tribalism and deep dysfunction we wrote about a year ago have not abated after the 2012 election. If anything, they have grown.

This year has produced only one substantial legislative achievement — a restructuring of the student loan program — while countless pressing matters have been blocked. Even where the Senate has shown impressive bipartisanship, as with the farm bill, enactment has been stymied by a House so entrenched on the far right that even urgent laws are bogged down. The same has been true of immigration reform. These last days of summer presage a fall and winter of ugly confrontation.

American politics is not just worse than it looks. It’s even worse than we thought.

Read more Outlook essays by Mann and Ornstein:

Let’s just say it: The Republicans are the problem

Want to end partisan politics? Here’s what won’t work — and what will.

Five myths about the 112th Congress

Five myths about the sequester

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