Agreeing to disagree

Is there anyone out there who isn't fed up with the photos of Pedro Sánchez and Pablo Iglesias, standing side-by-side and grinning robotically after signing their governing pact this week? Yes, they're making an effort to resolve the political deadlock that Sunday's election looked set to continue, but two questions now arise. First, if it was so easy for Sánchez's Socialists (the PSOE) and Iglesias' leftist Unidas Podemos (UP) to collaborate this time, why didn't they do so after the 28 April election, thus saving Spaniards from going to the polls for the fourth time in as many years? And secondly, how will this coalition - which will still be 21 seats short of a majority - actually function and who will be given what roles within it?

One thing that's already clear is that the deputy prime ministerial positions in the proposed PSOE-UP setup will be very different from each other. In a move clearly intended to assuage Brussels, Sánchez announced that acting Economy minister Nadia Calviño, Budget Director at the EU Commission from 2014 to 2018, will become deputy prime minister for economic affairs (essentially a rebranding of her current job).

The caretaking Socialist prime minister has also said that Iglesias will take another of the deputy prime ministerial roles - an appointment he was reluctant to make after the April election, but which has been added as an extra incentive for the UP president this time around. Not at all bad for the leader of the party that came in fourth on Sunday, with just 12.8% of the national vote!

Iglesias looked awkward in front of the cameras on Tuesday, and for good reason: up until now, he's occupied a cushy position on the fringes of power, from which he criticised the right and left wings of the establishment without having to govern or form legislation himself. Now, in a sudden and suspicious reversal on Sánchez's part, he's being welcomed into the political establishment and asked to assume the responsibilities of government.

Yet it's questionable whether Iglesias will prove ideologically flexible enough to work with the more centrist Socialists. It's not obvious, either, why Sánchez is apparently unconcerned about the two parties' differences - which was precisely the reason he refused to team up with UP after 28 April.

Particularly on economic issues, Iglesias is further to the left than Sánchez and is likely to push for levels of public spending that even the Socialist leader would be uncomfortable with.

Sánchez said at the press conference on Tuesday that "the political project [between the PSOE and UP] is so exciting that it overcomes any difference between us".

But the messy realities of coalition rule, especially between two forces that have previously resisted a partnership, might bring those differences into much sharper focus than they are now.