Polls suggest there are between one in three and one in four Americans who would believe anything. More than a third thought President George Bush did a good job during Hurricane Katrina; half of those thought he was excellent.

Throughout most of 2008, as the economy careered into depression, just over one in four believed Bush was handling the economy well. As Bush prepared to leave office in January 2009, bequeathing bank bailouts, rampant unemployment, and Iraq and Afghanistan in tatters, a quarter of the country approved of his presidency.

These are national polls that span the political spectrum. So you can imagine how concentrated the distortions become when filtered through the tainted lens of the right. A poll earlier this month revealed that a quarter of Republicans believe a community rights organisation called Acorn will try to steal the election for Barack Obama next year, while 31% aren't sure whether it will or not. It won't. Because Acorn does not exist. It was defunded and disbanded after a successful sting operation by conservatives a couple of years ago.

Meanwhile, a poll last month showed that a majority of Republicans likely to vote in the primaries still believe Obama was not born in the United States. He was. But no number of verified birth certificates will convince them.

Such is the nature of the electorate that will select Obama's principal opponent for the 2012 election. And such is the reason why a viable Republican contender has yet to emerge despite trough-loads of money and the Republican successes of the mid-terms. Among Republicans the latest polls suggest a crowded, splintered field of possibles with Mike Huckabee leading on 19%, followed by Mitt Romney on 15%, Sarah Palin on 12% and Newt Gingrich on 10%.

And if Republicans are unconvinced, Democrats are untroubled. When Obama is pitted against any of them in six states he took from Republicans in 2008, polls suggest he would win all but one – he would lose to Huckabee in North Carolina by 1%. He fares best against Palin, trouncing her by double figures everywhere but Ohio. Despite his favourability ratings suggesting the nation is evenly divided on his job performance, a national Pew poll suggests 47% would back Obama's re-election against 37% who would prefer a Republican and 16% who did not know.

The challenge for the primaries is neither new nor unique to the right. The tension between appealing to the base and to moderates is the perennial test of any successful candidate in national United States politics. To win the party nomination you must appeal to your motivated base. To take the country as a whole you generally must engage the wavering centre.

What is relatively new, however, is the level of logical dysfunction and hyperbole within the American right, trapped in a fetid media ecosystem where all the Kool-Aid has been spiked. In short, what you need to say and do to be credible within the Republican party essentially deprives you of credibility outside it. The Republicans seem to realise this, but like an obese glutton at an all-you-can-eat buffet, they just can't seem to help themselves.

When asked which of their possible contenders they believe to be qualified for the job they can think of one, Mitt Romney, and even then barely 50% believe so. The person they say they like the most, Sarah Palin, is also the one they believe is least qualified: only 29% believe she can actually do the job.

This was evident in Iowa, the state that holds the first caucuses in theprimary process next year, where many of the possible candidates converged over the weekend. On Friday, at a forum for Iowa pastors called "Rediscovering God in America", Mississippi governor Haley Barbour, an outsider, vowed to do "everything that we can to stop abortion". The next day at the Conservative Principles Conference, where Barbour spoke, abortion didn't come up. "It is absolutely critical that we elect a new president," he said. "I think the best way, perhaps the only way, is for us to make sure the 2012 campaign is focused on policy." He added: "The American people agree with us on policy."

When it comes to Libya, Newt Gingrich has vacillated from "Exercise a no-fly zone this evening", on Fox News 12 days before bombing started, to "I would not have intervened" four days afterwards. Meanwhile, congresswoman Michele Bachmann, who once called for an investigation of "anti-American" lawmakers, told the conference: "It can't just be a Republican. Do you hear me? It can't just be a Republican." She urged Iowa conservatives to set the tone for the nation, saying: "We need to have people who have guts, who you won't see melt like wax when they get there."

Some feared that Iowa, which holds such a crucial role in the nomination process, could be too extreme to pick a competitive candidate. "We look like Camp Christian out here," Doug Gross, a Republican activist and former nominee for governor, told the New York Times. "If Iowa becomes some extraneous rightwing outpost, you have to question whether it is going to be a good place to vet your presidential candidates."

Strategically the division between social and fiscal conservatism has largely been settled. With just a few exceptions only social conservatives (anti-abortion, anti-gay marriage, pro-gun) can get elected within the Republican party, so it has ceased to be much of an issue in primaries. Once nominated, candidates stress only fiscal conservatism for fear of scaring away centrists. Once elected they emphasise both, evidenced by the growing efforts to restrict access to abortion by legislators who barely raised the issue of abortion on the stump.

When I saw Rand Paul speak before 35 people in Leitchfield, Kentucky, just over a year ago, he never mentioned abortion, and nor did anyone else. "I'm not running for preacher," he told me. "I'm running for office." Now he's a senator who supports slashing aid to planned parenthood. Meanwhile, the Kentucky legislature has recently passed a bill requiring a woman to view an ultrasound before she has an abortion.

But the strategic question of where and how to strike a balance between principle and pragmatism, or even whether such a balance is desirable, still eludes them. So too does any consensus on the kind of facts – Obama's religion and place of birth being just the two most obvious – that would enable others to take them seriously.

With little more than 18 months to go before the election there is still time for a candidate to emerge who can fudge the difference and straddle the divide. An event like the Arizona shootings might also force a reckoning between the right and reality. But generally speaking, incumbent presidents lose elections; challengers don't win them. Obama is vulnerable on many fronts. With unemployment still high, poverty and home repossessions growing, Guantánamo still open, two old wars not yet over and a new one just begun, he deserves more than token opposition. There is just over a third of the country who think that Republicans are providing it. But then they believe anything.