It all began with the apparent predictions of the pollsters. It's that time of the political moment when all the opinion polling companies and organisations get busier than the politicians. This year was going to be no different. Day in day out the polls kept coming in. According to opinion polls, it was a very tightly and closely fought election like no other. It was neck and neck they said. It was going to be another hung parliament and the list went on and on. It was meant to be the most unpredictable election in modern history, yet it was the most predictable election in opinion polling history. WHAT HAPPENED? the polls were wrong!How pollsters gravely underestimated conservative support in 2015 and risked the entire integrity of the opinion poll industry.Those that follow polling closely will recall the famous situation in 1992 where the polls appeared to point to a Labour victory (of sorts) only for the Conservatives to prevail. Since that time, much work has gone into correcting those mistakes and subsequent election results have shown that the polling industry has been largely successful at achieving this.However, in an election so close, with so many different parties (and pollsters) involved, could we face the prospect of history repeating itself? Here I examine some of the challenges pollsters face.It's very closeAside from the occasional poll showing a 6 point lead for Labour or the Conservatives, most national polls show the two main parties neck and neck. In fact, the current UK Polling Report average has Labour and the Conservatives on 34 points each. Therefore, by understating either the Labour or Conservative vote slightly, the polls could point to a completely different result to the one we see on Election Day. Indeed, some pollsters could easily call the election wrong (or right) by sheer accident of 'margin of error'. What is clear is that the apparent closeness of the race exacerbates the potential for the polls to be 'wrong'.