Politics is a bruising, full-contact sport -- as Ronald Reagan discovered shortly after his inauguration.

In his autobiography, An American Life, he tells how he and Nancy hosted a dinner party for House Speaker Tip O'Neill and his wife -- "a warm, pleasant evening" filled with laughter and stories. Reagan felt he'd made a friend.

"But a day or two later," he writes, "I picked up a newspaper and read a story in which Tip really lit into me personally because he didn't like the economic recovery program and some of the cuts I proposed in spending. Some of his remarks were pretty nasty. ... I called him and said, 'Tip, I just read in the paper what you said about me yesterday. I thought we had a pretty fine relationship going.'"

"Ol' buddy," Tip said, "that's politics. After six o'clock we can be friends, but before six, it's politics."

More than 25 years later, the tone in Washington is no better. Hearing the invective fly on cable news talk shows, watching lawmakers denounce each other on C-SPAN, reading the outrage that fills our op-ed pages -- it's enough to make anyone cry "Enough!" No wonder voters keep telling politicians they're fed up with partisanship -- or that candidates include obligatory calls for "unity" in their stump speeches.

But is unity really possible? Those who are too nice, one assumes, will get steamrolled by opponents willing to "go negative," while those who are too mean contribute to the poisonous atmosphere that upsets everyone in the first place. But before you throw your hands up in despair, let me suggest you read the intriguing new book Common Ground: How to Stop the Partisan War That Is Destroying America by Cal Thomas and Bob Beckel.

Yes, that Cal Thomas and that Bob Beckel -- who, as they freely admit, contributed to that climate of polarization. "We helped write the game plan, and we have participated in everything from getting money out of true believers to appearing on television to help spread the contentious message," they write. "In many cases, we wrote the message. We know the jig, and it's just about up." (The book's title, incidentally, comes from a USA Today column they've been writing for the last two years.)

In short, Thomas and Beckel know a thing or two about polarization. And if they can come together and chart a course for "common ground," there's no excuse for the rest of us to keep sniping at each other.

Now, at a time when book titles range from Rush Limbaugh is a Big Fat Idiot to If Democrats Had Any Brains, They'd Be Republicans, it takes guts to write a book called Common Ground. In politics, you don't win points by playing nice. But, folks, we're talking about Cal Thomas and Bob Beckel. Even when they're encouraging the rest of us to get along, they do it in a, well, sort of friendly contentious manner.

Common Ground also provides a solid overview of the political history of the last three decades. This gives their views some important context, as we move from the days of Richard Nixon (whose "charisma level had the depth of floor wax, but without the shine") through the Carter, Reagan, Bush 41 and Clinton presidencies. We see how the bare-knuckled fight over the nomination of Robert Bork to the Supreme Court pushed the divide between Right and Left to new heights (or lows) of ugliness.

Thomas and Beckel don't spare Congress. Their bill of indictment includes time that House Ways and Means Committee Chairman Bill Thomas called the police to evict Democrats from the committee library (where they had adjourned in the wake of a hearing-room protest). They note how Senate Majority Leader Harry Reid torpedoed a bipartisan effort to pass immigration reform. Almost everywhere you turn, you find policymakers on both sides of the aisle turning up the heat in a take-no-prisoners style of debate that leaves everyone bitter and angry.

Yes, we must expose evil intent, misguided policy and bad ideas for what they are. But as my boss, Ed Feulner, president of The Heritage Foundation, constantly says, we must take care not to make the attacks personal. In an inspiring speech titled "Lay Your Hammer Down," delivered at Hillsdale College in 2004, Feulner said: "Our free, self-governing society requires an open exchange of ideas, which in turn requires a certain level of civility rooted in mutual respect for each other's opinions and viewpoints."

As far as Thomas and Beckel are concerned, now is the ideal time to work at promoting civil discussion:

"The 2008 presidential campaign is the most wide-open race in recent history. For the first time since 1924, neither a president nor a current or former vice president is competing for either party's nomination. At the same time, both parties are facing an identity crisis; Democrats are adjusting to their new status as the congressional majority party, while Republicans face a presidential season without their traditional party-establishment front-runner."

But can this work in today's red-state/blue-state America? Absolutely -- in large measure, Thomas and Beckel argue, because the famous red-blue dichotomy is a myth. Some so-called red states have elected liberal Democrats, while some alleged blue states have pulled the lever for conservative Republicans.

What matters, in the end, is how we respond to their call for civility. As they write: "So, what will it be: More combat, leading to more anger and a perpetuation of our broken political system, or common ground? The question should answer itself." Let's hope so.

Rebecca Hagelin, a vice president at The Heritage Foundation, is the author of "Home Invasion: Protecting Your Family in a Culture That's Gone Stark Raving Mad" and runs the Web site HomeInvasion.org.