Sen. Charles Grassley was grumping as usual on MSNBC on Monday morning (“the government is a predator, not a competitor”) when journalist Chuck Todd interrupted his rap with a serious question. If the Senate Finance Committee’s bipartisan Gang of Six comes up with a compromise that you think is a good deal, Todd asked Grassley, “are you willing to be one of just three or four Republicans” to support that deal?

No, Grassley answered immediately. “It isn’t a good deal if I can’t sell my product to more Republicans. We have to find a broad base of support within the Republican Party.”

Why, then, does Max Baucus, the committee’s Democratic chairman, persist in the charade of bipartisan negotiations with Grassley? Does he — does anybody — really believe that a Republican Party so deeply invested in defeating President Obama’s campaign for health-care reform is open to a scaled-down version that Obama can still claim as a victory? On Tuesday, the Republican Senate whip, Jon Kyl of Arizona, called Democrat Kent Conrad’s proposal for cooperatives in lieu of a public option “a Trojan horse” for a government takeover of health care. Hard to find the green shoots of compromise in that response.

Hard to believe, in fact, that they’ll ever be found, given the increasing rigidity, insularity and extremism of today’s Republican Party. The problem is that the GOP is no longer a truly national party in its geographical composition or its ideological breadth. Throughout U.S. history, our two major political parties have usually contained multitudes and contradicted themselves accordingly. For much of the 20th century, the Democrats were the party of the white South, the immigrant North and labor unions. The Republicans were the party of Wall Street bankers, Main Street merchants, professionals and Sun Belt cowboys.

But today’s Palinoidal Republicans have lost most of the professionals, much of Wall Street and an increasing chunk of suburbia. What they can claim is the allegiance of the white South and the almost entirely white, non-urban parts of the Mountain West.

Of the 40 Republican members of the Senate, fully half — 20 — come from the old Confederacy, the Civil War border states where slavery was legal or Oklahoma, which politically is an extension of Texas without Texas’ racial minorities. Ten others come from the Mountain West. The rest of the nation — that is, of course, most of the nation — has become an ever-smaller share of Republican ranks.

All parties are home to distinct subcultures with distinct beliefs. What’s different about today’s GOP is that increasingly, it is home to just one, and a whole sector of the media — Fox News, talk radio — makes its money by emphasizing this subculture’s sense of separateness, grievance and alarm, and by creating its own set of “facts.”

Asked in late July whether they believed Barack Obama was born in the United States, 93 percent of Democrats and 83 percent of independents said yes, but just 42 percent of Republicans agreed. Behind those numbers, 93 percent, 90 percent and 87 percent of Northeasterners, Midwesterners and Westerners, respectively, said yes, but just 47 percent of Southerners said they believed the president was born in this country.

Obama, the Republican base is saying, personifies an America that is increasingly alien to them. It’s multiracial, as they are not. It puts Sonia Sotomayor, who sure doesn’t come from their America, on the Supreme Court. Increasingly, the Republicans have descended into white identity politics.

Republican ideology has shrunk alongside its geography and demographics. Where once its view of the role of government ran the gamut from Rockefeller activism to Goldwater libertarianism, today the party largely adheres to the religiosity and the anti-statism of the white South. (In its ideological uniformity, today’s GOP looks — O, the irony — more like a classic European party than an American one.)

In short, the Republican Party with which Democrats could make deals no longer exists. The GOP is too narrow; the gap between the parties, too wide. Our politics are not those of the mid-20th century, when bipartisanship was fairly common. If anything, they’re more like those of the mid-19th century, before the Civil War, when North and South combined only to make a house divided against itself — a conflict resolved not by compromise, but, as Lincoln predicted, by a nation then half-slave and half-free becoming “all one thing or all the other.”

Lincoln’s prophecy still holds. Our current conflicts may be resolved only as the South becomes traditionally less Southern and more diverse — home to more Northern transplants and immigrants.

That process was already at work in the 2008 elections, when Obama carried Virginia, North Carolina and Florida on the strength of those demographic shifts. As that process continues — perhaps only as it continues — the course of reform in America may run more smoothly.

Meyerson is editor-at-large of American Prospect and the L.A. Weekly.