In "Dover Beach", Matthew Arnold lamented that although Victorian England was full of people who paid lip-service to the Christian faith, religion itself was in retreat:
The Sea of Faith
Was once, too, at the full, and round earth's shore
Lay like the folds of a bright girdle furl'd.
But now I only hear
Its melancholy, long, withdrawing roar . . .
The sound in the background of US politics for the past 40 years has been the melancholy, long, withdrawing roar of liberalism, and in its place, the arrival of a different, perhaps more discordant sound - of a conservative movement unlike any other around the world. Conservatives in America now control the presidency, both houses of Congress, most of the state legislatures and governorships; and they will probably continue to drive America to the right, even if they lose the White House.
This is not to deny that America has liberals (as it insists on calling its leftists). It has millions of them, and they don't just dwell in Manhattan and San Francisco. Go deep into Bush country and you will find vibrant liberal outposts in conservative states such as Texas (Austin), Colorado (Boulder) and Georgia (Athens). Nor is it to deny that there have been some significant reversals for the right during the past 40 years - including Watergate and the Clinton presidency. But there is little doubt who has been winning the argument. Only one in five Americans accepts the moniker "liberal"; 40 per cent like to be called conservatives.
You can argue that America has always had a conservative strand. Founded by churches and commercial companies, it has never had a proper socialist movement. In the 19th century, Friedrich Engels derided it as being "so purely bourgeois" that his creed had no hope of surviving there. Summoned by Joseph Stalin to Moscow in 1929, Jay Lovestone, the head of the American Communist Party, offered broadly the same excuse.
All the same, the fact is that, in the 1950s, conservatism was a minority creed - an odd collection of McCarthyites, southern feudalists and marginal intellectuals. The Republican Party was in thrall to the east coast elite. Accused once of being a conservative, Dwight D Eisenhower angrily said he was a right-thinking liberal like everyone else. Richard Nixon and John F Kennedy ran on broadly the same Europhile, big-government platform in the 1960 election. Lyndon Johnson tried to Europeanise the country through the Great Society programme (whose title, incidentally, was stolen from a British socialist, Graham Wallas).
When the young Ronald Reagan began to question the New Deal liberalism of his youth, he had to search in some fairly exotic places - such as Fred Schwarz's School of Anti-Communism and the Freedom Forum bookshops, where you could buy Schwarz's book You Can Trust the Communists (to be Communists). And the first portent of modern American conservatism - Barry Goldwater's presidential campaign of 1964 - resulted in the biggest ever victory for the Democrats.
Yet the Goldwater insurgency, founded on a profound antagonism towards government and rooted in the south and the west, was a sign that something plainly was happening. In the 1960s and 1970s, conservative America began to build an electoral coalition and, more importantly, the set of ideas that now dominates US politics. Leftists tend to attribute the Republican rise to the party's capture of the southern white vote. But although there was certainly a racial tinge to Nixon's southern strategy, the rise of American conservatism over the past four decades is a wider story.
Across the country, the Republican Party has managed to convince blue-collar voters that it shares their values, not just on racial issues such as affirmative action, but on gay marriage, taxes and abortion, for example. There is a certain brutal logic, within a country that has always liked capitalism, religion and patriotism, in positioning yourself as the more capitalistic, more religious and patriotic party. Over the past 40 years, the Republicans have whittled down the Democrats' once huge lead in party registration.
And it is not just a matter of protecting the past; it is having ideas about the future. American conservatism is usually derided in Europe for being right-wing. In many ways, however, it is a much more liberal creed than British Toryism: it has no respect for hierarchy, let alone feudalism; it is also much more optimistic. Unlike the Tories, the Republicans have their bastions in the newer parts of the country - the south and the west; the party has flourished among the strip malls and the subdivisions.
In the past decade alone, some $1bn has gone into conservative think-tanks such as the Heritage Foundation and the American Enterprise, Hudson and Cato Institutes. But the new "rive droite" also includes magazines such as the National Review and the Weekly Standard, Fox News and 500 Christian TV stations, anti-tax clubs, pro-gun and pro-family groups - and this network stretches to every state in the Union. In the north-west, Washington State is firmly Democratic, but still boasts several large right-wing think-tanks, notably the Discovery Institute and the powerful pro-gun Second Amendment Foundation, as well as property-rights groups and many social-conservative organisations.
This is the foundry that has produced many of the ideas which are now part of our lives - from pre-emptive action through welfare reform to broken-windows policing. This right-wing establishment has pushed American political discourse to the right, just as the Fabians, organised by Sidney and Beatrice Webb, managed to push Britain to the left. Look at any significant debate - over the size of government, over defence spending, foreign policy, crime and punishment, inequality - and you find that America now takes a recognisably more right-wing view than does Europe. Indeed, America no longer seems keen to try to Europeanise itself in the same way as it did in the 1960s.
There are two standard rejoinders to the idea that the right is in control in America - and they come broadly in the shape of Bill Clinton and John Kerry. In fact, both men only prove the ascendancy of the right. Clinton was as close to being a conservative killer as American liberalism has yet invented. It was not just a matter of charm and political instinct: he championed an attempt to rethink the American left. He was a new Democrat who had accepted globalisation.
Yet what did the Clinton administration achieve? The first two-term Democrat president since Franklin D Roosevelt will be remembered for proclaiming the end of big government, reforming welfare and balancing the budget. Whenever Clinton drifted to the left - for instance, over gays in the military or his wife's healthcare plan - he was punished. Soon he was reduced to wailing that he was merely an Eisenhower Republican.
As for John Kerry, the "Massachusetts liberal" could well win the coming election. But then, he is running against a president who is promoting an unpopular war; who has lost several million jobs; who, even by American standards, has drifted pretty far to the right; and who, as the televised debates showed, is less than Ciceronian in defending that record. In such circumstances, any Democrat would be competition. The question is whether a Kerry victory would mark a reversal of the right.
Most of the evidence points to a pause at best - and not just because President Kerry would probably have to deal with a Republican Congress. Unlike Clinton, Kerry has made no attempt to rethink liberalism; his pitch is merely that he is not George W Bush. At home, he has accepted the bulk of Bush's tax cuts; he will rescind only the reductions for people earning more than $200,000. Abroad, he will not join Kyoto or the International Criminal Court, he shows no signs of pulling out of Iraq any faster than Bush would, he has been a steadfast defender of Ariel Sharon and he has signed up to most of Bush's doctrine of pre-emption. Europeans should thus prepare to be disappointed.
The man whom the European left hopes will resuscitate American liberalism is a preppy war hero, who boasts about his record as a tough prosecutor and the number of guns he owns, who is married to a multimillionairess, who talks about his conservative values and who wanted John McCain to be his vice-president. You have only to imagine the impossibility of George Bush talking about his liberal values and asking Ted Kennedy to join his ticket to understand how far America has moved to the right.
That long, withdrawing roar is getting ever fainter.
John Micklethwait and Adrian Wooldridge, who work for the Economist, are the authors of The Right Nation: why America is different (Allen Lane, the Penguin Press)