YouGov/Sun - CON 33, LAB 38, LD 8, UKIP

This morning's YouGov poll for the Sun has topline figures of CON 33%, LAB 38%, LDEM 8%, UKIP 12%. It shows Labour's lead down to five points for the second YouGov poll in a row.

I suspect these are two polls at the lower end of the normal margin of error and the underlying average will still turn out to be a six or seven point lead, but all the same, the lead appears to be falling. As ever, any change in the lead invites explanation, something that polls are much less good at doing. My guess is that it is a reflection of the slight increase in economic optimism (or decrease in economic pessimism) that we've seen over the last couple of months, something that was perhaps masked a bit by the boost UKIP got from the local elections, but is becoming apparent now that the amount of publicity that UKIP are receiving has fallen a bit.

It is just a guess of course, and things are rarely explained by a single factor. I've seen some people ascribe it to Labour's economic announcements over recent weeks, though personally I don't think policy statements by opposition parties get noticed enough to have any real immediate effect on polls. Alternatively it could be the dividing lines emerging over welfare, or just the Conservative party avoiding being actively at each others throats for the last couple of weeks. It bottom line is that it's difficult to know what actually moves voting intention, my only advice is to avoid the mistake of assuming that it must be the issue that you care about that's done it.