WITH Susana Díaz beaming radiantly from the conference stage after winning control of the Spanish Socialists’ mighty Andalusian branch in Granada last month, fans hailed a generational and gender revolution in the party. Her victory confirmed that the energetic 39-year-old, who also runs the region’s government, is now Spain’s most powerful Socialist. That is a big role in a country where the ruling Popular Party (PP) of Mariano Rajoy and the Socialists tend to alternate in power. But is not so clear that she will lead the party into the next election.Ms Díaz’s smile hides an iron will. She is at ease with power and is reputedly ruthless against rivals. Spain’s fractious Socialists may need such qualities as they wander in the electoral wilderness, failing to turn 27% unemployment and fears about the future into votes. It is smaller parties which are cashing in on voter dismay; the Socialists still lag behind the PP, which ousted them in 2011 and may now reap the rewards of economic recovery.Can Ms Díaz change that? A recent poll made her the most popular candidate to lead her party into the 2015…