Sinn Fein are picking up votes because there's a good number of people who can't vote for Fianna Fail this time and won't vote for Labour or Fine Gael for class - Labour is very middle class and a bit West Brit - or historical reasons. Add in a bit of a nationalist leaning and you end up voting for Sinn Fein.

How much blame the EU is going to get is an interesting question.

The personal past may be more important for the chances of a Labour/Sinn Fein government than the political past. Many of the senior Labour figures come from the Democratic Left party which came from the Offical Sinn Fein movement and later merged into the Labour party.

The relationship between Official Sinn Fein and Provisional Sinn Fein - the Provisional IRA linked party that Adams is in - was less than entirely friendly. On the other hand, this is maybe the best chance ever for a Labour Taoiseach and to completely rewrite the rules of Irish politics, so I suspect that will be sufficient to overcome any of Labour's or Sinn Fein's objections. There's enough Labour supporters like me who would normally abhor Sinn Fein but are willing to hold our noses this time around, given the alternatives.