Four internet polls this week have suggested the referendum race – which today enters its fully regulated phase so far as campaign spending is concerned – continues to be very tight. Both YouGov (in one poll) and TNS put the two sides on 50% each (once Don’t Knows are left to one side) while with a 48% figure for Remain, ICM put support for staying in the EU below 50% for the first time. Meanwhile YouGov published a second poll that gave Remain no more than the narrowest of possible leads.

ICM’s data were weighted by reported probability of voting, which reduced the Remain share by one point. TNS did not include the responses given by those who initially said ‘Don’t Know’ but then said ‘Remain’ or ‘Leave’ in response to a follow-up question; if they had been included Remain would have been credited with 52%. But none of this dispels the impression that the contest is anything but close.

But what if we look underneath the bonnet? Is there any evidence that either side is making progress in persuading voters of the merits of their side of the argument, progress that might perhaps eventually bear fruit in the form a swing in vote intentions? Here it is the first of the YouGov polls (conducted for The Times) that is most illuminating. For it asked its respondents a series of questions about what they thought the consequences of remaining or leaving the EU would be, questions that the company previously asked in February (immediately after David Cameron had concluded his renegotiation of Britain’s terms of membership). We can thus see how much difference, if any, the last couple of months of campaigning has made to voters’ views on the issues.

In truth, neither side seems to have made much of an impression. For example, 31% now think we would be economically worse off if we left the EU while 24% reckon we would be better off. The figures are virtually identical to those last February when they were 31% and 23% respectively. Equally, at 32% the proportion who think it would be good for the NHS if we left the EU is little different now from the 30% that were of that view two months ago. Meanwhile there is an equally small increase, from 11% to 14%, in the proportion who think leaving would be bad for the NHS.

But there are a few instances where one side or the other has made progress. Immigration is now seemingly even more of a strong card for the Leave campaign. The proportion who think immigration would fall if we left now stands at 55%, up five points on February. Meanwhile, more surprisingly perhaps, there has been an increase, from 16% to 25%, in the proportion who feel that ‘we would be less at risk from terrorism’ if we left the EU (while the proportion who take the converse view remains at 10%). True, this is an issue on which most people (48%) are still to be convinced that remaining or leaving would make a difference either way. Nevertheless, the Prime Minister’s argument that the UK would be more ‘secure’ if it remained in the EU is not proving to be as persuasive as many Remain strategists seemingly assumed it would be.

However, one argument on which the Remain side has made marked progress is its claim that prices will go up if we leave the EU, a claim that features quite prominently in the government’s controversial information leaflet that is being distributed to all voters. Now 36% believe that prices would increase, up from 23% in February. Only 6% think that prices would fall as a result of leaving the EU, little different from the 8% who were previously of that view.

What these trends suggest is that while the two sides have made some progress on those issues on which they were already relatively strong in the eyes of voters, neither has had any success in counteracting its negatives. As a result, the arguments have become yet more evenly balanced in the eyes of voters. On the one hand they consider voting to remain in the EU to be the ‘safer’ bet economically. On the other hand, they regard leaving as the better way of ensuring that Britain’s borders and its health service are ‘protected’. Little wonder voters appear to be divided so evenly down the middle on which way to vote.