Last Friday, Orrin Hatch, the veteran Republican senator from Utah, announced that he would vote against the confirmation to our supreme court of judge Sonia Sotomayor. Hatch is a devout conservative, and Sotomayor seems pretty liberal, so on the face of it, you might say, so what? Here's what.

Hatch has been in the Senate for 32 years and has never voted against any president's high court nominee. True, most of the nominations in that time have been made by Republican presidents. But even so, Hatch's history means he has voted for two nominees who were obviously liberal, Ruth Bader Ginsburg and Stephen Breyer. Sotomayor's record does not mark her out as appreciably to their left, and in terms of years of service on the bench, she towers over them. So what's changed?

Hatch's decision reflects the degree to which, during the Obama era, American conservatism – already fiercely ideological and obstructionist, operating according to sets of "facts" produced and paid for by oil companies, pharmaceutical manufacturers and other corporate interests – has contrived to go completely barmy.

In most countries, you have two major political parties or broad factions. They disagree on many things. But both begin by accepting certain suppositions. I would imagine that in Britain, for instance, both Labour and the Tories think healthcare for all or at least most people is a good idea. They have different notions about how to do it, but the goal is agreed upon. I gather also that the Tories accept the basic idea that global warming exists and that man's actions have contributed to it.

But American conservatism does not believe healthcare for all or most is a desired outcome at all. Conservatives believe people are responsible for their own healthcare, and that people who don't have it just aren't showing enough pluck and initiative. Last Thursday, one Republican congressman announced that the party wouldn't even offer its own version of healthcare legislation – and this man runs the party's so-called Solutions Group! And on climate change, of course, most deny its existence, and all deny that human activity has played any role in it whatsoever.

I could give you 50 examples, but you get the idea. We have a party that lives in an alternate universe. Wondering why Obama and the Democrats are having trouble lately? They've committed their errors, and the party's genuine ideological diversity can make consensus hard to come by. But the big issue is this. The alternate-universe party represents the views of about 27% of the people, as nearly as I can tell. More will label themselves conservative in polls, but when you analyse the percentage of Americans who endorse the extreme views the GOP represents on a range of matters, it comes to a little more than quarter of the population. But the Republicans hold about 42% of the power in Washington, with the ability in Senate, according to that body's rules, to block almost anything, almost any time.

Let's return for a moment to Hatch. In his statement, he gave no actual reason for opposing Sotomayor. He'd reviewed her record and concluded – naturally, with "heavy heart" – that he could not support her. In the absence of stated reasons, we can speculate on some. Might fear of rightwing radio loudmouth Rush Limbaugh be a factor here? Might it have something to do with the fact that, the day before Hatch's statement, the National Rifle Association had announced that it would take senators' votes on Sotomayor into account in its future evaluations?

It's true that most Democrats opposed George Bush's last high court nominee, Samuel J Alito. If supreme court votes were the only measure, this would just be normal politics. But there are multiple signs of Republican psychosis. Obama has been compared to Hitler, Stalin, Mussolini, Charles Manson, a monkey (of course) and, in an image promoted last week, a witchdoctor – by a neurosurgeon no less, who has been a big opponent of healthcare reform.

Most conspicuously, there's the growing "birther" movement, people who believe that Obama is not a US citizen, doesn't meet the constitutional requirements for the presidency and must therefore be impeached. He was born in Hawaii in 1961. That makes him a citizen. His campaign last year released a copy of his birth certificate. But of course, for these folks, it's a forgery. There's even a video afoot "demonstrating" how the document was faked.

You might think people in positions of responsibility would try to reel these folks in a little. Instead, in the House of Representatives, a few Republicans have introduced a bill to require future presidential candidates to prove their citizenship, starting in 2012, when Obama will be seeking re-election.

Healthcare is socialism. Saving the auto industry is liberal fascism. Trying to halt global warming is both. Negotiating with Iran – I didn't even get to foreign policy – is proof that Obama wants to obliterate the US. And to top it all off, the Great Obliterator isn't even a citizen.

Obama has to try to conduct the business of state with people who believe or lend cover to all these notions. Trust me. Be glad you have your Tories.