The UK is plunged into a December election for the first time since 1923, and the dominant issue is, of course, Brexit.

Not that an election can ever be fought on one issue – and there is no shortage of other matters that feature in the campaign, from the state of public services in Britain after years of austerity, to the personality of the Prime Minister – a mini-Trump who does not hesitate to tell blatant lies on all fronts.

“If Conservatives do not secure a majority, then there will be a new referendum”

But Brexit dominates, with one bottom line: if the Conservatives secure a majority of seats in the Commons, then Brexit will happen next year. If they don’t, then there will be a new referendum – something to which every opposition party in the Commons (Labour, Liberal Democrats, Greens, Scottish Nationalists, Welsh Nationalists) are now committed.

A majority of the UK public would now vote in a referendum to remain in the EU, according to polls, but in the election there is a risk that that does not translate into a majority of seats for ‘Remain’ parties in the House of Commons.  With the non-proportional UK electoral system of single-member constituencies won by the candidate with the most votes (even if that is only 30% of the votes with the remainder spread over several parties), the Conservatives could win most seats with just a third of the votes.  That is because they are the main Brexit-supporting party, getting almost all the votes of Brexit supporters, while ‘Remain’ support is split over several parties. 

“Rather than pacts between the parties, it is the voters who are likely to lessen the effect of the divisions in the Remain camp.”

Electoral pacts between parties is almost unknown in the British tradition, and rules make it difficult to organise anyway. There has been a mini-pact for a limited number of seats between the LibDems, the Greens and the Welsh Nationalists, which they call the ‘Remain Alliance’, which is a misnomer as it targets some seats currently held by Remain-supporting Labour MPs, taking a risk that the seats in question fall to the Conservatives as a result. 
Rather than pacts between the parties, it is the voters who are likely to lessen the effect of the divisions in the Remain camp. This can be done through ‘tactical voting’, where voters rally behind the best placed candidate to defeat the Conservatives in any given constituency (likely to be the Labour candidate in most seats, others in some).  There are already several websites offering advice on that. So, we could see traditional LibDem voters voting Labour in northern seats, and traditional Labour voters voting LibDem in the Southwest, resulting in a greater chance of defeating the Conservative candidate. 
Not every ‘Remain’ voter is willing to do that.  Holding your nose and voting for a party you never normally would vote for is not appealing. But if enough people are willing to do so, just this once, it would help to defeat the Conservatives in many constituencies. 
On the other side of the equation is a possible division among Brexit supporting ‘Leave’ voters.  Nigel Farage has withdrawn the candidates of his ‘Brexit Party’ in all constituencies held by the Conservatives. But he is maintaining them in seats held by Labour. This will divide the ‘Leave’ vote in those constituencies, making it more difficult for the Conservatives to take the seat from Labour.  And remember: to win a majority in the House of Commons, Johnson needs to take seats from Labour, especially if, as expected, he loses seats in Scotland to the SNP.
Beyond tactical voting, there is, of course, the opportunity to win hearts and minds (and votes) by relentlessly drawing attention to the shortcomings of Johnson and his government and to the Labour party’s policy offers. The effect of so many ‘moderate’ Conservative MPs leaving the Conservative party and denouncing the right-wing takeover of it, may also have an effect on public perceptions. Johnson is also prone to gaffes. Anything can happen.