Leading article: The threat to American conservatism

It is always tempting to home in on the absurdity of the Republican right in America, the almost comic quality of some of their views and the ludicrous nature of the accusations they hurl at President Barack Obama.

The paranoid and hate-filled world of the "birthers", the Tea Party people and all the rest is so alien to the British experience as to be incomprehensible. We tend not to take them seriously, or assume that the Republicans' constant lurch to the right inevitably renders them unelectable. We may be making a mistake. The huge size of the rally held in Washington at the weekend – where several hundred thousand people turned up to hear the Fox News talk show host Glenn Beck announce that America was "turning back to God" – provides further disturbing proof, if any were needed, of the growing popularity of the hard right.

The fact that the rally was held on the site where Martin Luther King made his "I have a dream" speech 47 years ago has caused offence among the heirs of King's civil rights movement, who resent Mr Beck's assertion that the two causes have much in common. But ructions from that quarter will do Mr Beck and fellow star turn Sarah Palin no harm among their supporters. It is more likely to do the opposite. Overwhelmingly white, conservative, rural and religious, their constant complaint that they "want their country back" is in part a thinly-veiled snipe at Mr Obama's race.

Here on the other side of the Atlantic, we await two things: for so-called ordinary Americans to recoil from and disavow the right's toxic, divisive rhetoric; and for moderate Republicans to start re-asserting the very different traditions of Lincoln, Eisenhower, and George Bush senior, for that matter.

Neither of those outcomes seems to be materialising. Centrist Republicans have become a marginalised minority in their own party – eclipsed and somehow out of place among people who have come to expect references to God's will to appear in almost every sentence. Meanwhile, Obama's fellow Democrats are heading towards mid-term elections in November in a mood of despondency, and expect a drubbing at the hands of their adrenaline-filled opponents.

There is a real chance that the Democrats could lose control of the House of Representatives, in which case Mr Obama will serve out the rest of his term with both hands tied behind his back. He would still have a free-ish rein in foreign policy, but at home he would find every initiative blocked by opponents who have made it clear they are ready to cause total gridlock in pursuit of their aims. Moreover, if the Republicans do as well as expected in November, the right, as the ascendant force in the party, will claim all the credit for it, in which case the likes of Ms Palin will be well placed to obtain the Republican nomination.

Can Mr Obama turn this round? Yesterday, he was in New Orleans, marking the fifth anniversary of Hurricane Katrina, the mishandling of which blew a large hole in the presidency of George Bush junior. One would have thought memories of that highly divisive episode would remind most Americans of what they – then – wanted to escape from, which was having an ideological zealot rather than a cool-headed pragmatist as their president.

The man they chose as his successor remains what he was on day one; a decent, thoughtful patriot and a builder of bridges who still aspires to lead a country in which race is no longer the defining issue. He has given the country a measure of health reform and begun the process of disengagement from costly and unpopular military entanglements. He would appear an infinitely preferable choice as national leader to any of the friends of Glenn Beck. Yet nothing can be taken for granted, and in November we will see whether those who have hijacked the Republican Party have been halted in their tracks, or have more glory days ahead.