Who's winning? Nobody. An average of recent polls puts Remain two points in front but some of the most recent have shown Leave pulling ahead. Polls conducted by phone tend to show Remain further ahead while online polls usually put Leave in the lead. Campaigners on both sides agree the contest is very tight and neither side is confident of victory.

Should we trust the polls? Lord Hayward, the Conservatives' favourite psephologist, doesn't. He was one of the few to call last year's general election correctly, having concluded the polls were getting it wrong. He thinks they're wrong again about the referendum, overestimating support for Remain among some key groups.

So what will decide the outcome? Turnout. This has become a campaign of mobilisation rather than persuasion, with each side targeting messages at their own supporters more than at wavering voters. The Remain campaign is more sophisticated and disciplined and it is using the same micro-targeting technology that helped the Conservatives win last year's general election. Leave's greatest advantage is that its supporters are older and thus more likely to go out and vote than Remain's younger supporters. The voter registration website crashed this week. Is that a sign of high turnout? Yes. It crashed because of a surge of late registrations, mostly from younger voters. The government extended the registration deadline by 48 hours, amid grumbling from Leave campaigners who fear most of the latecomers will back Remain. A high turnout is seen as benefiting Remain, who probably need almost 60 per cent of voters to turn out for victory.

Which voters hold the key to victory? Labour supporters. Polls suggest that, with Conservatives split over the referendum, almost half of those who support Remain are Labour voters. But because so much of the debate has been between competing wings of the Conservative party, with David Cameron and Boris Johnson occupying the limelight, Labour is worried its supporters may think it has nothing to do with them.

Labour leader Jeremy Corbyn is a lukewarm Remain supporter, having opposed the EU throughout his entire political career until now. And some white working-class Labour voters are attracted by the Leave campaign's promise to control immigration.

How is immigration playing as an issue for Leave? Very well indeed. An Ipsos Mori poll this week found 63 per cent of voters believed leaving the EU would help to reduce immigration. This compares to just 25 per cent who believe Remain's core message, that Brexit would adversely affect their living standards. By linking the free movement of people within the EU to the housing shortage and pressure on public services such as health and education, the Leave campaign has made immigration its most effective issue.

What is Remain's main argument? That Brexit would put a bomb under the British economy. Every major international organisation and independent economic institute agrees that leaving the EU would have an adverse impact on the British economy, at least in the short term. Although voters are sceptical about some of the more bloodcurdling threats of economic meltdown, the warnings should help Remain. The Remain campaign hopes voters will be unwilling to take a risk with their economic well-being by voting for Brexit and will conclude the economic cost is too high a price to pay for controlling immigration.

What do the bookies say? Remain will win.