Spain’s caretaker prime minister, Mariano Rajoy, is due to seek parliament’s support for a second term on Tuesday but knows that his chances are slim.

“There is a serious risk of having to call a third election in the same year,” he warned supporters of his conservative People’s Party in Galicia this weekend.

Spaniards returned to the polls in June after the parties failed to put together a coalition government in the wake of the election in December. Neither major party commands an absolute majority, however, and the left-wing Socialists have said they will not vote for the right-wing Rajoy. If they refuse to budge, a third election may be inevitable.

Rajoy’s way out

Rajoy has the lukewarm support of the liberal Ciudadanos. But their 32 seats are not enough to put Rajoy, who has 137, over the top. He needs a majority of 176 — or, and this may be Rajoy’s way out, a simple majority of the voting deputies.

The Socialists would not vote for Rajoy but could abstain and thus enable him to stay in power with only active votes against him from the far left.

That’s still a big ask. The far-left Unidos Podemos is breathing down the Socialist Party’s neck and would undoubtedly seek to take advantage of a center-left “betrayal”. They almost overtook the Socialists as the largest party of the left in the last election. Polls for the next one are close.

Lesser of two evils

The specter of a Podemos victory is what should convince the Socialists to let Rajoy stay in office this time, Shaun Riordan, a former diplomat, has argued here. Many left-wing voters would hate it, but it’s the lesser of two evils. Losing the next election and being forced to prop up a Podemos-led government would be worse.

Not to mention that Podemos has some reckless ideas, from defaulting on Spain’s debts and renationalizing industries to overturning Rajoy’s labor reforms which have helped bring down unemployment.

The case for left-wing unity

Joop van den Berg, a Dutch political scientist, has made the opposite argument from Riordan (if not specifically about the situation in Spain).

He has argued that social democrats across Europe have the same problem: their traditional working-class base is defecting to populists either on the far left or the right while left-leaning professionals are tempted to switch to unambiguously cosmopolitan parties, like social liberals or Greens.

The only way to stop this hemorrhaging, says Van den Berg, is for social democrats to ally permanently with the other parties of the left.

In Spain’s case, that would mean the Socialists forming a block with the Unidos Podemos and Rajoy’s People’s Party allying with the Ciudadanos.

Problem is, none of the four parties are interested.