Britain’s smaller parties are on the march. Labour should win all of tomorrow’s three by-elections in Middlebrough, Croydon North and Rotherham. But Friday’s real story looks set to be further advances for smaller, newer non-establishment parties – especially Ukip on the right, and George Galloway’s Respect on the left.

Indeed, in Rotherham, where I’ve spent the last couple of days, there seems to be almost an unwritten pact between Ukip and Respect. Yesterday Lisa Duffy, the Ukip campaign director, told me that Labour were now out of it and that it was simply a fight between her party and Respect.

Then, later in the day, the Respect candidate, Yvonne Ridley, told me exactly the same thing. One might have thought they were carrying out a pincer movement on Labour. “We’re both trying to demolish the Labour vote,” says Ukip’s national chairman Steve Crowther.

These are exaggerated claims, of course. Labour must still be the front-runner in Rotherham, but of the three by-elections taking place tomorrow, Rotherham is the one which the party is most anxious about. That’s why Labour campaign boss Tom Watson was here today, along with party general secretary Iain McNicol and election stalwarts such as John Spellar.

Labour’s candidate, Sarah Champion, is clearly able, but her campaign is suffering big problems. Her first disadvantage, of course, is the scandal that caused this by-election. The previous MP, Labour’s Denis MacShane, resigned after being suspended from parliament for 12 months for fiddling his expenses (though not really for personal gain).

Then, Sarah Champion was not the candidate the local Labour party actually wanted. Activists in Rotherham would have preferred a local contender, and when the national Labour hierarchy forced them to choose from a shortlist of two women outsiders, dozens of people walked out in protest.

Finally, there’s been the big story this week of the Ukip foster parents who had their children taken away by the local Labour council because of the parents’ political affiliations.

It’s been a huge gift to Ukip nationally and to their local candidate, Jane Collins, a party organiser who already claims the remarkable achievement of coming second in last year’s by-election in nearby Barnsley Central. And while Ukip will hope to pick up disaffected Tories and white, working-class Labour supporters who are worried about immigration, Respect are concentrating their efforts on Rotherham’s substantial Asian population.

Both the government parties seem to be mounting token campaigns. Simon Wilson, the Tory nominee, refused to say if he agreed with David Cameron’s remark in 2006 that UKIP are “closet racists mostly”.

The Lib Dem, Michael Beckett, is an eccentric character who, if elected, would be the first male MP in a couple of centuries to wear a pony-tail. Would he cut it off if elected? I asked. “My wife wouldn’t let me,” he said. Mr Beckett’s campaign is such a token affair that he hasn’t even had a visit from Nick Clegg, even though the Lib Dem leader’s own seat is only a few miles away.

It’s been very cold these last couple of days in Rotherham. That, and the short daylight hours, could mean another miserable turnout to rival those in the PCC elections two weeks ago. These are the conditions for Labour do poorly, and small protest parties to perform exceptionally well.

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