To be sure, it was enjoyable watching Representative Devin Nunes, a Republican of California, warn that by passing health reform, Democrats “will finally lay the cornerstone of their socialist utopia on the backs of the American people.” Gosh, that sounds uncomfortable. And it’s been a hoot watching Mitt Romney squirm as he tries to distance himself from a plan that, as he knows full well, is nearly identical to the reform he himself pushed through as governor of Massachusetts. His best shot was declaring that enacting reform was an “unconscionable abuse of power,” a “historic usurpation of the legislative process” — presumably because the legislative process isn’t supposed to include things like “votes” in which the majority prevails.

A side observation: one Republican talking point has been that Democrats had no right to pass a bill facing overwhelming public disapproval. As it happens, the Constitution says nothing about opinion polls trumping the right and duty of elected officials to make decisions based on what they perceive as the merits. But in any case, the message from the polls is much more ambiguous than opponents of reform claim: While many Americans disapprove of Obamacare, a significant number do so because they feel that it doesn’t go far enough. And a Gallup poll taken after health reform’s enactment showed the public, by a modest but significant margin, seeming pleased that it passed.

But back to the main theme. What has been really striking has been the eliminationist rhetoric of the G.O.P., coming not from some radical fringe but from the party’s leaders. John Boehner, the House minority leader, declared that the passage of health reform was “Armageddon.” The Republican National Committee put out a fund-raising appeal that included a picture of Nancy Pelosi, the speaker of the House, surrounded by flames, while the committee’s chairman declared that it was time to put Ms. Pelosi on “the firing line.” And Sarah Palin put out a map literally putting Democratic lawmakers in the cross hairs of a rifle sight.

All of this goes far beyond politics as usual. Democrats had a lot of harsh things to say about former President George W. Bush — but you’ll search in vain for anything comparably menacing, anything that even hinted at an appeal to violence, from members of Congress, let alone senior party officials.

No, to find anything like what we’re seeing now you have to go back to the last time a Democrat was president. Like President Obama, Bill Clinton faced a G.O.P. that denied his legitimacy — Dick Armey, the second-ranking House Republican (and now a Tea Party leader) referred to him as “your president.” Threats were common: President Clinton, declared Senator Jesse Helms of North Carolina, “better watch out if he comes down here. He’d better have a bodyguard.” (Helms later expressed regrets over the remark — but only after a media firestorm.) And once they controlled Congress, Republicans tried to govern as if they held the White House, too, eventually shutting down the federal government in an attempt to bully Mr. Clinton into submission.

Mr. Obama seems to have sincerely believed that he would face a different reception. And he made a real try at bipartisanship, nearly losing his chance at health reform by frittering away months in a vain attempt to get a few Republicans on board. At this point, however, it’s clear that any Democratic president will face total opposition from a Republican Party that is completely dominated by right-wing extremists.

For today’s G.O.P. is, fully and finally, the party of Ronald Reagan — not Reagan the pragmatic politician, who could and did strike deals with Democrats, but Reagan the antigovernment fanatic, who warned that Medicare would destroy American freedom. It’s a party that sees modest efforts to improve Americans’ economic and health security not merely as unwise, but as monstrous. It’s a party in which paranoid fantasies about the other side — Obama is a socialist, Democrats have totalitarian ambitions — are mainstream. And, as a result, it’s a party that fundamentally doesn’t accept anyone else’s right to govern.

In the short run, Republican extremism may be good for Democrats, to the extent that it prompts a voter backlash. But in the long run, it’s a very bad thing for America. We need to have two reasonable, rational parties in this country. And right now we don’t.