A conservative MP's bizarre voting error, which allowed the left-wing government to save its labour market reform at the last minute, caused a political storm in Spain on Friday, with the opposition considering taking the matter to court.
An "abuse of power" and an "unforgivable democratic error": this is how the right-wing Popular Party described the vote that allowed the Spanish Congress to validate this emblematic text on Thursday, by 175 votes to 174.
In a letter published on Friday, Casero said that he had been told that he would not be allowed to vote for the reform, but that he wanted to vote against it.
The Conservative MP, who was ill and voting remotely, said he realised he had made a mistake when he received his electronic voting "certificate". He then went to the Parliament to ask to vote again, without success.
"The president was informed before the start of the vote that a deputy wanted to exercise his right, by voting in person, because there had been a problem with the electronic voting system," insisted Popular Party leader Pablo Casado.
"The rules of the Congress clearly state that in this type of situation", the Parliament's governing body "must meet to take a decision", Casado insisted, assuring that in "other cases" similar to this, the vote had been "cancelled".
In addition to the voting error, other unusual events marked Thursday's vote, which took place against a backdrop of high tension as the government failed to win the support of some of its traditional allies, such as the Catalan pro-independence group ERC.
Two deputies from the small right-wing Union of the People of Navarre (UPN) opposed the text, although they had pledged to vote for it - in accordance with their party's instructions, a "betrayal" denounced by the left.
At the crucial moment of the announcement of the result, the president of the Congress, the socialist Meritxell Batet, stated in the hemicycle the rejection of the reform, before changing her mind. This reversal was greeted with dismay by the opposition and relief by the government.
The adoption of the reform, intended to reduce the precariousness of the labour market, was one of the conditions set by Brussels for the payment of part of the European recovery plan, of which Madrid is one of the main beneficiaries with €140 billion.
Negotiated for months by the government, this text came into force on 1 January as part of an agreement sealed with employers and unions. But it had to get the green light from Congress in order to be definitively validated.
In the aftermath of this turbulent vote, the Popular Party promised to "fight to the bitter end" to have the vote invalidated.
Alberto Casero, the 43-year-old MP at the heart of the scandal, who was previously unknown to the general public, has become the object of much mockery on social networks, where some have ironically elevated him to the rank of hero of the left.
The Socialist Party (PSOE) denounced an "overreaction" and advised the Popular Party - which initially referred to a "computer error" - "to teach its members to vote electronically".
"There has never been a technical failure in electronic voting, never," Adriana Lastra, deputy secretary-general of the PSOE, insisted at a press conference, denouncing a "Trumpist" manoeuvre by the PP - in reference to the allegations of fraud made by Donald Trump in the 2020 US elections.
For Javier Pérez Royo, a professor of constitutional law at the University of Seville, there is virtually no chance of the text being re-voted and of the courts taking up the issue.
The MP "would have to be able to show that there was really an error in the way the system worked and that seems impossible. It is a system that has been used hundreds of times with the pandemic," he said on La Sexta television.