In winning the 52 parliamentary seats in the Nov. 10 national election, Vox became Spain’s third-largest political party.

The election, the country’s fourth in four years, underlined the fragmentation and polarization of Spanish politics, with the ultranationalist Vox making the clearest gains. With no party close to a parliamentary majority, Pedro Sánchez, the caretaker Socialist prime minister, is negotiating the formation of a new government in a coalition with another left-wing party, Unidas Podemos. Parliament must still approve what would be a minority government.

The gender violence law that Vox wants repealed was passed in 2004 under a new Socialist government led by Prime Minister José Luis Rodríguez Zapatero. At the time, the law was considered groundbreaking, and was part of a broader overhaul of the country’s social legislation. The following year, Spain became one of the first Western countries to legalize same-sex marriage.

The law took several steps to help protect women. It set up special courts to handle their cases. It made it easier for women to report violence, notably by using a specific toll-free number. And it toughened sentences for offenders and made it harder for them to later come into contact with their victims.

Violence against women in Spain, however, remains a serious problem. Over a thousand women have been reported killed since statistics were first officially gathered in 2003. Last year, women reported almost 167,000 cases of domestic violence, while the courts issued more than 39,000 restraining orders.

On Monday, a man was alleged to have killed his partner on the Spanish island of Tenerife, which is part of the Canary archipelago, raising the total number of women killed in Spain this year to 52. According to Spanish news reports, the woman was killed after her partner grabbed a knife from her grandmother, who had tried to intervene after she heard her granddaughter shouting for help.

Since the gender violence law came into force, it has been challenged about 200 times in court as unconstitutional. Vox has been unsparing in its criticism, describing the law as “the pact of shame,” and arguing that it violates the right to equality inscribed in the Spanish Constitution.