The worst thing you can do in analysing polls of voting intention is to get excited at polls that show something exciting and different and ignore those that show the same old pattern. Occassionally the unusual poll will herald a genuine movement in public opinion – after all, whenever there is a change, one poll has to pick it up first. More often than not, the unusual poll will turn out to be a freak result, the product of unusual sampling or methods. If there is genuinely a change in public opinion, other polls will pick it up sooner or later, so it’s always wise to withhold your judgement.

Today we have one of those unusual polls, and we have the overexcitement you’d expect. ICM’s monthly poll in the Guardian has topline figures of CON 39%(+3), LAB 33%(-2), LDEM 8%(nc), UKIP 7%(-2), GRN 7%(+3) (tabs). This is pretty odd all round – a storming six point lead for the Tories, up on thirty-nine percent; the Greens and UKIP equal on seven percent.

In the Guardian’s write up they are rightly dubious, and include a welcome caveat from ICM’s Martin Boon about the inevitability of random variation and the sample perhaps being a touch too Tory. I’ll just leave it with the usual caveats – it’s one poll, and an odd looking one at that. Sure, it could be the start of some Tory surge, but if it is we will see it echoed in other polls today…and luckily enough we have at least three of them.

Populus this morning had topline figures of CON 33%, LAB 33%, LDEM 8%, UKIP 15%, GRN 5% (tabs). The Conservatives are up two points (possibly helped by an update in weighting targets), but no big tory lead.

Still to come are the weekly Ashcroft poll and the daily YouGov poll. Come the end of the day, the way to judge where we are is too look at all them as a whole – not fixate on the unusual one.

UPDATE: Lord Ashcroft’s weekly poll has topline figures of CON 33%(-3), LAB 33%(-1), LDEM 9%(+3), UKIP 13%(+3), GRN 6%(-1). Changes are from a fortnight ago – Ashcroft took a week off to avoid bank holiday fieldwork. As with today’s Populus poll, there is nothing here to support the big Tory lead in the ICM poll. Full details are on Lord Ashcroft’s website here.

UPDATE2: Finally the daily YouGov poll for the Sun has topline figures of CON 33%, LAB 34%, LD 8%, UKIP 13%, GRN 6% – a one point Labour lead. Putting all four polls together that ICM poll looks very much like an outlier. Such things are an unavoidable part of polling – and well done to Guardian for reporting it in a heavily caveated way within the context of other polls showing no movement, rather than getting all excited about it.