On the day of writing (Thursday), Spain's congress is voting on whether to extend its phaseout of nuclear power beyond the provisional deadline of 2035. The result will be non-binding - but if it's in favour of extension, the pressure will increase on Pedro Sánchez, who has already been urged by industry leaders to reconsider the phaseout. The backdrop to the vote is an EU-wide debate about renewables versus nuclear that has already become politicised, less than two weeks after Spain and Portugal's historic blackout.

The pro-atomic faction argues that Spain needs more nuclear energy in its system, to guarantee supply when less predictable sources such as wind and solar fail. Sweden's energy minister Ebba Busch, of the centre-right Christian Democrats, warned other EU members this week of making the "Spanish mistake" - i.e. not having enough nuclear baseload on their national grids. "If you want a lot of power and you want it to be fossil-free," she said, "then nuclear is your pick."

Sánchez and the rest of Team Green argue that there is no evidence to pin the blame on renewables, and that nuclear energy also disconnected last Monday, along with wind and solar. In a speech on Wednesday, the Socialist leader highlighted the incoherence of demanding an explanation of the blackout as well as claiming to have the solution to Europe's energy problems. If you don't know the exact cause of the generation gap (Spain's grid operator hasn't worked it out yet), how can you know how to fix the problem?

Sánchez committed a similar error in the blackout's immediate aftermath. Last week, he said the cause was unknown, that he wasn't ruling out any hypotheses - but that renewables definitely weren't to blame. Commitment to either side of the renewables v atomic debate, it seems, is primarily ideological. Many participants pick a side, then look for evidence to support their position, rather than the other way around.

This raises the question of whether any investigation into the causes of Spain's blackout can be free from bias. As one anonymous diplomat told Politico this week: "I already heard some saying that we cannot blame renewables because it would not be politically correct. This would be a horrible and harmful approach."

For this reason, the PP has called for an independent parliamentary investigation into the outage, in addition to the one being undertaken by Sánchez's government (which we know in advance won't find fault with renewables). Portugal's prime minister, meanwhile, has called on the EU to conduct its own inquiry. Both of these investigations are likely to be less biased than the Spanish government's - but of course, they could also be used to push pro- or anti-green agendas. The nuclear option, unlike Spain's national grid at 12.33pm last Monday, is a highly charged issue.