BY the time you read this, one of two things will have happened. In the first scenario, Craig and Brian MacDonald will have been voted off The X Factor, their eight-week campaign to offend the human ear ending with last night's extraordinary rendition of Shang-A-Lang. Or else, the brothers from Ayrshire will have made it into the next round, flying in the face of critical opinion and proving, if proof were needed, that the British people are always willing to throw a bone to an underdog, even when said mutt would be better off muzzled, neutered and locked in a burning kennel. If The MacDonald Brothers have made it through another week of the reality show then they are truly the greatest survival story to come out of Alloway since Tam o' Shanter cantered over the River Doon.

For those who don't know, these two young lads - a former bank clerk (Craig) and bed salesman (Brian) - are amiable, modest and straightforward. They live with their mum and until recently made a living singing at wedding receptions, performing classic pop hits augmented by fiddle and accordion. Yet since their involvement in The X Factor, and especially in the last few weeks, the MacDonalds have become curiously iconic, particularly in Scotland, where they were recently mobbed in the Ayr branch of Asda. They may be pish but - by Wallace's beard - they're oor pish!

The big tabloids are right behind them. The Scottish Sun has styled itself as "the official paper of The MacDonald Brothers" - a kind of Pravda meets Smash Hits arrangement. The Daily Record has also been cheerleading, albeit with reservations; showbiz editor Rick Fulton recently claimed that were they to get a record deal - The X Factor offers a £1 million contract as a prize - their CDs would be bought by people who were looking for an act somewhere between Daniel O'Donnell and Michael Ball. Lexicographers have confirmed that this is the exact definition of faint praise.

The so-called quality press are not immune to their charms either. A recent Scotsman editorial opined that with our rugby team being so soundly beaten by Australia, "Scotland's self-respect rests heavily on the shoulders of the MacDonald brothers" and noted that MSPs get only half the votes that the singing duo have received each week.

This last comment is part of a trend among pundits to link the MacDonalds with politics. A Guardian writer has called for England to declare war on Scotland in an effort to stop Scots voting MacDonald, and in what was intended as a more serious point, Sun columnist Martel Maxwell claimed that the brothers' success is an expression of the same nationalist feeling that could lead to Scottish independence. "The MacDonalds are in the right place at the right time," she wrote. "They've unwittingly tapped into a feeling of unrest among their countrymen. A feeling that the time is ripe for change."

Blimey. How has it come to this? As with so many of the ills of modern life, Simon Cowell is to blame. He loathes The MacDonald Brothers, and has not been shy of saying so on live television. Week by week he has slated them as "totally forgettable", "totally mediocre", "utterly pointless" and "dreary". When they sang Sailing, in red T-shirts and kilts, he said: "I hope Rod Stewart was watching with the sound turned down. It was verging on insane, that performance."

To spite Cowell, the British public has been voting to keep the MacDonalds in the competition. Organisers of The X Factor do not release information on voting patterns, but it seems likely that the majority of their votes have come from Scotland. They certainly have a nucleus of support in the clubhouse of Brunston Castle golf course, an Ayrshire venue at which the MacDonalds regularly perform. The club's owners and their five grown-up children are said to have been casting over 2000 telephone votes each week.

They are not alone in their passion. The catalyst for the Scottish vote came when Cowell was accused of anti-Scottish bias after deliberately referring to the MacDonalds as "the McDougall brothers". He also sneered that their version of Abba's Fernando was "very Scottish", when it would have been less inflammatory and more accurate to have said "very rubbish".

The brothers accept that Cowell's animosity has worked in their favour, but, rather sweetly, Craig MacDonald believes that the high-waisted pop svengali may in fact have a hidden agenda; that he secretly wants them to win. "Simon Cowell has been in this business a long time, and if he was looking to get us out of the competition then he's went the wrong way about it," the lighter-haired brother tells me (a few days before last night's vote), down the line from the X Factor studio in London. "I don't know whether maybe he's seen the potential in us from the beginning and wants us to do well and keep improving. Our feeling is that maybe he is giving such negative comments because it makes us determined to work harder. We don't really know what's going on in Simon's mind. It's a funny one but it has helped us a bit."

Not that they have found Cowell's comments easy. "The first few weeks, it was absolutely terrible," says Craig. "We actually thought about walking away from the competition. We thought we were never going to win with him doing that to us. We felt we couldn't take it any more and it knocked our confidence so much."

His little brother Brian, who turned 20 last Tuesday, admits that he found it tougher than Craig. "You never saw it on TV because I managed to hold myself together until I got off camera, and then I'd go to the toilet and have a wee cry to myself," he says. "It does get to you. Everybody's trying to do their best, and when he starts ripping into you in front of 10 million viewers it's hard to get that out of your head. But I really am having a good time now after seven weeks of grief."

Craig explains that the turning point came in the fifth week of the live show. "We sang the Robbie Williams song She's The One and felt it was a really good performance. So when Simon said it was terrible we just decided we didn't care what we thought any more," he says. "We decided to stay in the competition, let the criticism go over our heads, and concentrate on our performances. The public are voting for us. They're lifting the phones and spending money to keep us in the show. It wouldn't have been fair to walk away after them giving us so much support."

In England, the media are largely against The MacDonald Brothers - the Guardian television critic Charlie Brooker called them "sinister and horrible, like a pair of haunted porcelain dolls who've suddenly come alive on the sideboard" - but the public has been increasingly on their side, and, by the end of last week, they seemed to be building momentum, particularly among teenage girls, who are a key demographic.

Writing on a hormonally charged fan-site, Donna from Wimbledon says it best: "You boys are all I can think about at the moment. Whenever I close my eyes, you're there serenading me with your beautiful voices. I could certainly walk 500 miles if it meant being nearer to you, Craig. I've been having this recurring dream recently where we are both dancing in the Scottish glens, drinking whisky and eating haggis smeared on oatcakes. You're wearing your kilt and then you get down on your knees and ask me to marry you. I'm still hoping that this dream will come true. I think you are definitely going to win The X Factor and I will be supporting you 100%. I've even had a T-shirt printed with your lovely faces on, and am currently learning to speak Scottish."

Given such intense support, can they actually triumph? Even assuming that last night Britain had the sense to dump awful Ray Quinn (a tiny KD Lang crossed with a crotch-thrusting Eddie Munster) and keep the MacDonalds in the running, it still seems unlikely. The final takes place on December 16 and most people expect that it will be a battle between Ben Mills, who sings like a hungover howler monkey undergoing a tracheotomy, and Leona Lewis, who sounds like Mariah Carey and may well be an android.

"If Ray goes out, then The MacDonald Brothers will be the favourite to get evicted next," says Rupert Adams, spokesman for bookies William Hill. "There can be little doubt that Ben and Leona will contest the final. That said, the Scottish vote has been greatly underestimated week after week, so we have done very well out of eviction betting."

Tom Urie, the Scottish actor and musician who recently starred as Danny McGlone in the stage version of Tutti Frutti, is a staunch supporter of the brothers. In the week that they performed The Proclaimers song I'm Gonna Be (500 Miles), he voted 18 times by text and had his land-line on redial. "I'd love The MacDonald Brothers to win but I don't think it'll happen," he says. "Not if they've got Barry Manilow songs this week. The show is becoming an easy-listening nightmare. Why don't they have a Babyshambles week? Or do Pulp songs? Just something a little more modern and interesting. Give them a real challenge instead of something clichd and boring like Love Is All Around that they've sung at karaoke for the last 10 years.

"When they did 500 Miles, you could see they were really into it. That is exactly what these guys should be doing. They should be folk heroes and that's how Scotland will get behind them."

The MacDonalds consider their Proclaimers cover to have been a risk that paid off. Even Simon Cowell liked it. If they are still in the running, their strategy now, when it comes to choosing songs, will be to try and play the Scottish card without alienating middle England (although Brian MacDonald tells me that if he had his way they'd be performing Metallica's One). It must help that the Caledonian vote is no longer split, fellow Scots Nikitta Angus and Kerry McGregor having left the show.

Assuming they are still in it this morning, do the MacDonalds honestly believe they can win the whole contest? "Of course we do," says Craig. "Our aim now is to reach the final, then once we get there that's another matter and we'll see how far we can go. Everybody in the competition now has a good chance. Nobody can predict who is going to go out. When Eton Road and Ben Mills were in the bottom two, that was a total shocker. We just have to concentrate on working hard. That's all we can do."

Their mentor Louis Walsh believes they can go all the way. "If we get them in the final we can win," he declares (again, speaking before last night's crucial vote). "They've never been in the bottom two, everybody loves them, the country is behind them and they are getting better."

Asked whether he actually thinks his protegs are any cop, Walsh prefers to point out their commercial potential. "I think they will sell an awful lot of records in the middle of the road market," he says. "They can sell records to mammies and daddies in the way that people like Westlife do I like them. I picked them for my final four because I thought they were good. I felt they would appeal to people who like Robson and Jerome, The Everly Brothers, The Righteous Brothers, people like that. There's a market there but nobody is tapping into it." He says that even if they don't win The X Factor, he will try to get them a recording deal.

Of course, he has another reason for wanting the MacDonalds to triumph, and it has nothing to do with money. "Cowell will be so furious. He's lost so much face already and will have egg all over his face. He said that never in a million years were they ever going to win the competition and I want to prove him wrong."

It has been a long, strange trip for the brothers. They didn't actually apply to go on The X Factor; a friend submitted a form on their behalf. But having succeeded in becoming one of the final few acts - out of around 100,000 applications - they have given it their all. In their life before reality TV, they were multi-instrumentalists who wrote their own material - pop/rock with a Celtic tinge - and would like to get the chance to start releasing albums.

"This has been the best experience I've ever had in my life," says Brian. "It's the most pressure I have ever felt, but it's made me a stronger person. If we are lucky enough to get into the music industry at the top level then this has been the best preparation we could ever have - dealing with criticism and performing in front of large audiences.

"I love performing and singing. My dream is to be a recording artist and go on tour and do all that. I want it badly and that's what keeps me going. I know I've got this one shot, and no matter what we are just going to try to go all the way to the end."

The X Factor is on STV on Saturdays at 6.40pm. The MacDonald Brothers will be appearing as part of The X Factor live tour, which comes to the Aberdeen AECC on February 18 and 19, and the Glasgow SECC on March 4