Susana Díaz, the president of Spain’s most populous region, has formally announced her candidacy for the leadership of the opposition Socialist Party, telling supporters in Madrid, “We will win and we will govern.”

Díaz represents the pragmatic wing of the party. She faces two more left-wing opponents: Pedro Sánchez, the former party leader, and Patxi López, the former president of the Basque Country.

Of the two, Sánchez is the most serious challenger. If he prevails, the Socialists could adopt a more adversarial approach to the minority right-wing government of Mariano Rajoy.

If Díaz wins the leadership election, her party would likely continue to cooperate with Rajoy on crucial legislation.

180,000 Socialist Party members will decide in May.

Plot

Díaz, who leads the regional government of Andalusia, has the support of the Socialist Party machine. She was the driving force behind a coup against Sánchez last year, after he lost the election to Rajoy a second time.

Left-wing voters split their support between the Socialists and the anti-establishment Podemos movement. Fearing further defections to the far left, Sánchez refused a deal with Rajoy that would allow the conservatives to stay in power.

Díaz and other party leaders worried that Sánchez’ intransigence could cost them support from moderate voters and plotted to remove him.

Rajoy was subsequently confirmed to a second term. Sánchez still retains support from the party grassroots.

Hearts and minds

Díaz’ challenge will be convincing the Socialists they can only get back into power by clinging to the center.

Sánchez argues that the party ought to win back young and disillusioned voters from Podemos instead.

A similar struggle between hearts and minds played out in Podemos itself this year.

The party’s deputy leader, Iñigo Errejón, moved against longtime leader Pablo Iglesias in February on a platform of accommodation with the center-left.

Iglesias prevailed on a commitment to hard-left principle, which could keep Podemos in opposition so long as it fails to win an absolute majority.

Support

Polls show support for the mainstream Socialists has changed little from the 22 percent they won in the most recent election.

Rajoy’s conservatives are polling north of 30 percent, enough for a plurality but not an outright majority of the seats in parliament.

Podemos splits the remainder with the centrist Ciudadanos and regional parties.