The SNP is likely to win upwards of 30 seats at the election. Ukip is tipped to win around three. So why are both parties often treated as if they’ll have equal influence in the next parliament?

It’s a favourite habit of the London-based media. Andrew Marr did it last Sunday, when he opened his BBC programme by bracketing together guests Alex Salmond and Nigel Farage as “the insurgents” and “Britain’s possible kingmakers”, implying a parity of reach and ambition.

This is misleading.

Numerically, Ukip could well end up with around one tenth the number of SNP MPs in the new House of Commons. Even if the Conservatives are the largest party, the extra two or three votes that would come from a deal with Ukip would not be enough to build the foundation of a secure administration. I can’t believe David Cameron would want to be in such a position – at least, not in the long term.

None of the websites offering regular forecasts of the election result are predicting Ukip to win more than a tiny number of MPs. The Guardian is the most generous, suggesting the party will win four seats. Electionsetc.com is saying three, while May2015.com is saying five: Clacton, Rochester & Strood, Thurrock, Thanet South and Eastleigh. ElectionForecast.co.uk is currently the most cautious, predicting Ukip to win just one constituency.

Meanwhile the latest odds from Ladbrokes are for Ukip to win 4.5 seats. This means there are four seats where the party is currently favourite (though they don’t mention which) and one where it is tied.

Basically, no one is – as yet – anticipating Ukip to come anywhere near the “double figures” that Nigel Farage stated when he appeared on ITV’s Loose Women earlier this month. As for the 25 or 30 seats that won headlines last autumn, that particular spiral of sensationalism seemed to have completely fizzled out. In so far as forecasts are concerned, the Ukip deflation game is definitely under way.

The reverse is true for the SNP. I’ve lost count of the number of opinion polls done in Scotland whose results have been translated into headlines proclaiming a Labour “wipeout“.

As usual, I’d urge a lot of caution when trying to extrapolate anything at all about the election result from an opinion poll. There will not be uniform swings on polling day. The assumption behind the “wipeout” headlines is that the entire electorate of Scotland will behave in exactly the same way. This won’t happen. My instinct is that Labour will lose at least half of its Scottish seats to the SNP, but I’m wary of saying with confidence how many more will fall.

I may be wrong, of course, but with the SNP – as with Ukip – I find it more judicious to underestimate rather than overestimate. One thing feels clear, however. The SNP and Ukip are not psephological equals, and shouldn’t be treated as such. To do otherwise is to create a rather lopsided narrative for the remainder of the election campaign, albeit one that allows personalities like Salmond and Farage plenty of room to generate mini news-cycles on a Sunday morning. Which is perhaps the point.