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

Rep. Allen West, a Florida Republican, was recently captured on video asserting that there are “78 to 81” Democrats in Congress who are members of the Communist Party. Of course, it’s not unusual for some renegade lawmaker from either side of the aisle to say something outrageous. What made West’s comment — right out of the McCarthyite playbook of the 1950s — so striking was the almost complete lack of condemnation from Republican congressional leaders or other major party figures, including the remaining presidential candidates.

It’s not that the GOP leadership agrees with West; it is that such extreme remarks and views are now taken for granted.

We have been studying Washington politics and Congress for more than 40 years, and never have we seen them this dysfunctional. In our past writings, we have criticized both parties when we believed it was warranted. Today, however, we have no choice but to acknowledge that the core of the problem lies with the Republican Party.

The GOP has become an insurgent outlier in American politics. It is ideologically extreme; scornful of compromise; unmoved by conventional understanding of facts, evidence and science; and dismissive of the legitimacy of its political opposition.

When one party moves this far from the mainstream, it makes it nearly impossible for the political system to deal constructively with the country’s challenges.

“Both sides do it” or “There is plenty of blame to go around” are the traditional refuges for an American news media intent on proving its lack of bias, while political scientists prefer generality and neutrality when discussing partisan polarization. Many self-styled bipartisan groups, in their search for common ground, propose solutions that move both sides to the center, a strategy that is simply untenable when one side is so far out of reach.

It is clear that the center of gravity in the Republican Party has shifted sharply to the right. Its once-legendary moderate and center-right legislators in the House and the Senate — think Bob Michel, Mickey Edwards, John Danforth, Chuck Hagel — are virtually extinct.

The post-McGovern Democratic Party, by contrast, while losing the bulk of its conservative Dixiecrat contingent in the decades after the civil rights revolution, has retained a more diverse base. Since the Clinton presidency, it has hewed to the center-left on issues from welfare reform to fiscal policy. While the Democrats may have moved from their 40-yard line to their 25, the Republicans have gone from their 40 to somewhere behind their goal post.

What happened? Of course, there were larger forces at work beyond the realignment of the South. They included the mobilization of social conservatives after the 1973 Roe v. Wade decision, the anti-tax movement launched in 1978 by California’s Proposition 13, the rise of conservative talk radio after a congressional pay raise in 1989, and the emergence of Fox News and right-wing blogs. But the real move to the bedrock right starts with two names: Newt Gingrich and Grover Norquist.

From the day he entered Congress in 1979, Gingrich had a strategy to create a Republican majority in the House: convincing voters that the institution was so corrupt that anyone would be better than the incumbents, especially those in the Democratic majority. It took him 16 years, but by bringing ethics charges against Democratic leaders; provoking them into overreactions that enraged Republicans and united them to vote against Democratic initiatives; exploiting scandals to create even more public disgust with politicians; and then recruiting GOP candidates around the country to run against Washington, Democrats and Congress, Gingrich accomplished his goal.

Ironically, after becoming speaker, Gingrich wanted to enhance Congress’s reputation and was content to compromise with President Bill Clinton when it served his interests. But the forces Gingrich unleashed destroyed whatever comity existed across party lines, activated an extreme and virulently anti-Washington base — most recently represented by tea party activists — and helped drive moderate Republicans out of Congress. (Some of his progeny, elected in the early 1990s, moved to the Senate and polarized its culture in the same way.)

Norquist, meanwhile, founded Americans for Tax Reform in 1985 and rolled out his Taxpayer Protection Pledge the following year. The pledge, which binds its signers to never support a tax increase (that includes closing tax loopholes), had been signed as of last year by 238 of the 242 House Republicans and 41 of the 47 GOP senators, according to ATR. The Norquist tax pledge has led to other pledges, on issues such as climate change, that create additional litmus tests that box in moderates and make cross-party coalitions nearly impossible. For Republicans concerned about a primary challenge from the right, the failure to sign such pledges is simply too risky.

Today, thanks to the GOP, compromise has gone out the window in Washington. In the first two years of the Obama administration, nearly every presidential initiative met with vehement, rancorous and unanimous Republican opposition in the House and the Senate, followed by efforts to delegitimize the results and repeal the policies. The filibuster, once relegated to a handful of major national issues in a given Congress, became a routine weapon of obstruction, applied even to widely supported bills or presidential nominations. And Republicans in the Senate have abused the confirmation process to block any and every nominee to posts such as the head of the Consumer Financial Protection Bureau, solely to keep laws that were legitimately enacted from being implemented.

In the third and now fourth years of the Obama presidency, divided government has produced something closer to complete gridlock than we have ever seen in our time in Washington, with partisan divides even leading last year to America’s first credit downgrade.

On financial stabilization and economic recovery, on deficits and debt, on climate change and health-care reform, Republicans have been the force behind the widening ideological gaps and the strategic use of partisanship. In the presidential campaign and in Congress, GOP leaders have embraced fanciful policies on taxes and spending, kowtowing to their party’s most strident voices.

Republicans often dismiss nonpartisan analyses of the nature of problems and the impact of policies when those assessments don’t fit their ideology. In the face of the deepest economic downturn since the Great Depression, the party’s leaders and their outside acolytes insisted on obeisance to a supply-side view of economic growth — thus fulfilling Norquist’s pledge — while ignoring contrary considerations.

The results can border on the absurd: In early 2009, several of the eight Republican co-sponsors of a bipartisan health-care reform plan dropped their support; by early 2010, the others had turned on their own proposal so that there would be zero GOP backing for any bill that came within a mile of Obama’s reform initiative. As one co-sponsor, Sen. Lamar Alexander (R-Tenn.), told The Washington Post’s Ezra Klein: “I liked it because it was bipartisan. I wouldn’t have voted for it.”

And seven Republican co-sponsors of a Senate resolution to create a debt-reduction panel voted in January 2010 against their own resolution, solely to keep it from getting to the 60-vote threshold Republicans demanded and thus denying the president a seeming victory.

This attitude filters down far deeper than the party leadership. Rank-and-file GOP voters endorse the strategy that the party’s elites have adopted, eschewing compromise to solve problems and insisting on principle, even if it leads to gridlock. Democratic voters, by contrast, along with self-identified independents, are more likely to favor deal-making over deadlock.

Democrats are hardly blameless, and they have their own extreme wing and their own predilection for hardball politics. But these tendencies do not routinely veer outside the normal bounds of robust politics. If anything, under the presidencies of Clinton and Obama, the Democrats have become more of a status-quo party. They are centrist protectors of government, reluctantly willing to revamp programs and trim retirement and health benefits to maintain its central commitments in the face of fiscal pressures.

No doubt, Democrats were not exactly warm and fuzzy toward George W. Bush during his presidency. But recall that they worked hand in glove with the Republican president on the No Child Left Behind Act, provided crucial votes in the Senate for his tax cuts, joined with Republicans for all the steps taken after the Sept. 11, 2001, attacks and supplied the key votes for the Bush administration’s financial bailout at the height of the economic crisis in 2008. The difference is striking.

The GOP’s evolution has become too much for some longtime Republicans. Former senator Chuck Hagel of Nebraska called his party “irresponsible” in an interview with the Financial Times in August, at the height of the debt-ceiling battle. “I think the Republican Party is captive to political movements that are very ideological, that are very narrow,” he said. “I’ve never seen so much intolerance as I see today in American politics.”

And Mike Lofgren, a veteran Republican congressional staffer, wrote an anguished diatribe last year about why he was ending his career on the Hill after nearly three decades. “The Republican Party is becoming less and less like a traditional political party in a representative democracy and becoming more like an apocalyptic cult, or one of the intensely ideological authoritarian parties of 20th century Europe,” he wrote on the Truthout website.

Shortly before Rep. West went off the rails with his accusations of communism in the Democratic Party, political scientists Keith Poole and Howard Rosenthal, who have long tracked historical trends in political polarization, said their studies of congressional votes found that Republicans are now more conservative than they have been in more than a century. Their data show a dramatic uptick in polarization, mostly caused by the sharp rightward move of the GOP.

If our democracy is to regain its health and vitality, the culture and ideological center of the Republican Party must change. In the short run, without a massive (and unlikely) across-the-board rejection of the GOP at the polls, that will not happen. If anything, Washington’s ideological divide will probably grow after the 2012 elections.

In the House, some of the remaining centrist and conservative “Blue Dog” Democrats have been targeted for extinction by redistricting, while even ardent tea party Republicans, such as freshman Rep. Alan Nunnelee (Miss.), have faced primary challenges from the right for being too accommodationist. And Mitt Romney’s rhetoric and positions offer no indication that he would govern differently if his party captures the White House and both chambers of Congress.

We understand the values of mainstream journalists, including the effort to report both sides of a story. But a balanced treatment of an unbalanced phenomenon distorts reality. If the political dynamics of Washington are unlikely to change anytime soon, at least we should change the way that reality is portrayed to the public.

Our advice to the press: Don’t seek professional safety through the even-handed, unfiltered presentation of opposing views. Which politician is telling the truth? Who is taking hostages, at what risks and to what ends?

Also, stop lending legitimacy to Senate filibusters by treating a 60-vote hurdle as routine. The framers certainly didn’t intend it to be. Report individual senators’ abusive use of holds and identify every time the minority party uses a filibuster to kill a bill or nomination with majority support.

Look ahead to the likely consequences of voters’ choices in the November elections. How would the candidates govern? What could they accomplish? What differences can people expect from a unified Republican or Democratic government, or one divided between the parties?

In the end, while the press can make certain political choices understandable, it is up to voters to decide. If they can punish ideological extremism at the polls and look skeptically upon candidates who profess to reject all dialogue and bargaining with opponents, then an insurgent outlier party will have some impetus to return to the center. Otherwise, our politics will get worse before it gets better.

Thomas E. Mann is a senior fellow at the Brookings Institution, and Norman J. Ornstein is a resident scholar at the American Enterprise Institute. This essay is adapted from their book “It’s Even Worse Than It Looks: How the American Constitutional System Collided With the New Politics of Extremism,” which will be available Tuesday.