In a binary referendum like the one we're having at the moment each side will in effect be coalitions of different motivations. This is my reading of each side:
Bremain coalition1. Those that believe a federal European superstate is a good idea and that the UK should be subsumed within such a creation (people who are probably in this camp are journalist Polly Toynbee, Tories Ken Clarke and Michael Heseltine and Labour's Tony Blair (who always wanted the UK to adopt the Euro)).
2. Those that think the superstate is inevitable and that the UK may as well stay in the EU to try to influence it as much as possible into the British way of thinking. That's probably the bulk of pro-EU Conservatives and most Labour MP's too with the leader of the Remain campaign Alan Johnson likely to be a member.
3. The next group are those that don't have an opinion on whether the Eurozone is heading towards a superstate or not (or who simply don't believe that is what is happening) but worry that a Brexit may damage the UK economy leading to a recession. They also worry about the UK being isolated in the world. This is the group that David Cameron and Lynton Crosby believe will win the campaign for them because it's likely to include a lot of the current don't knows.
Brexit coalition1. The xenophobic element who dislikes Johnny Foreigner. These are likely to be older people who mainly live in southern England and are staunch Conservative voters.
2. Those that believe immigration is the number one issue in this referendum and believe that leaving the EU will bring back control to the numbers of people coming into this country. Michael Gove's idea of an Australian style points system will strongly appeal to this group (including my mate from work who I play golf with who ironically enough was born in Hong Kong and only came over here when he was 7
).
3. The third group are the ones that believe national sovereignty is the number one issue of this referendum. They are strongly against the UK becoming absorbed into a European superstate (or even being heavily involved in the way it operates while staying outside it's core). Like me they may have originally been a supporter of the UK becoming a member of the EEC but have turned against it when it's federalising tendency became clear in the late 1980's (Norman Tebbit, Frank Field and David Owen are likely to be in this group).
This is the group that I belong to.