When she first heard of a project to exhume and identify the remains of hundreds of Civil War victims — her grandfather possibly among them — Ángela Raya Fernández said she was “filled with hope, a lot of hope.”

Ever since she was a girl, she had heard stories about how her father’s father, José Raya Hurtado, was executed during the Spanish Civil War, his body ignominiously dumped in a ravine by forces loyal to Gen. Francisco Franco. She had only ever known him from black-and-white photos: round glasses, a receding hairline and a resolute gaze.

“We’ve long hoped that somebody could find him and give him a dignified burial,” said Ms. Raya, a soft-spoken, 62-year-old librarian.

But with general elections Sunday and polls predicting a right-wing victory, Ms. Raya and her family, along with thousands of others, fear that years of efforts to find their loved ones may suddenly grind to a halt.

The conservative Popular Party, which grew partly from Francoist roots, has pledged to repeal a memory law passed last autumn under the current Socialist prime minister, Pedro Sánchez, aimed at accelerating the exhumations. A possible alliance between the conservatives and the far-right Vox party, which has long opposed attempts to address the crimes of the past, has only heightened these fears.

“It would be a catastrophe,” Ms. Raya said, “a huge step backward.”

The to and fro over the memory law reflects how the traumas of Spain’s 1936-39 Civil War and Franco’s subsequent dictatorship, which ended with his death in 1975, still divide the country today.

To some, Franco, a nationalist, consolidated Spain’s postwar economic growth and served as an anti-Communist bulwark. To many others, his rule was one of repression, marked by mass executions, exile for thousands and the abduction of children.

An estimated 100,000 people were executed by Franco’s supporters during and after the Civil War, and buried in more than 2,000 mass graves scattered across the country.

No one dared disturb those sites in a country where Franco’s legacy has long been left unexamined. Conservatives, in particular, have argued that exhumations would only reopen old wounds.

For the left, the silence has been anything but therapeutic, even enraging. During the dictatorship, Spaniards were forbidden to talk about the killings. An amnesty law, passed in 1977, hoped to draw a line under the crimes of the past, but in effect made forgetting a crucial part of the effort to heal a divided nation in transition to democracy.

“It was a culture of silence,” said Agustín Gómez Jiménez, 49, a health worker who recounted how his father had long refused to even show a picture of his own father, executed in 1936.

Mr. Gómez said it took his sister rummaging through their father’s belongings to finally find some pictures, five years ago. One of them shows their grandfather on a beach, holding hands with his small, soon-to-be-orphaned son. “I have goose bumps just thinking my father hid the photos. He was so traumatized,” he said.

The first efforts to deal with the mass graves began in 2007, when a center-left prime minister, José Luis Rodríguez Zapatero, passed a “law of historical memory” that lent government support to exhumations.

But the legislation was slow to take effect and when the conservative Popular Party took power in 2011, the conservatives promptly defunded the law.

It took another decade, the commitment of Spanish left-wing-controlled regions and last year’s law — which created a census and a national DNA bank to help locate and identify the remains — for the exhumations to finally gain momentum.

Such efforts are evident in Viznar, a small, whitewashed village perched in the mountains overlooking Granada. For three years, a team of archaeologists has been digging in the ravine where Ms. Raya’s and Mr. Gómez’s grandfathers were buried along with about 280 other victims, including possibly the Spanish poet Federico García Lorca.

On a recent morning, the researchers were hunched over a 3-by-13-foot pit, using brushes and small blades to delicately remove the earth covering eight skeletons. Their spines and femurs were interlaced, a sign that bodies had been dumped one upon the other. Several skulls were pierced by round holes, evidence that the victims had been shot in the head.

“It’s a page of our history that was blank and that we’re writing today,” said Francisco Carrión Méndez, the archaeologist coordinating the project, standing beside the grave. Many relatives, he explained, want to find their loved ones and rebury them because “their dignity was stolen.”

Mr. Carrión pointed to photos of the victims that families had hung on nearby pines: a university rector with slicked-back hair; an imposing-looking barmaid. “They shouldn’t be forgotten,” he said.

Not everyone agrees. At the entrance of the ravine, a sign paying tribute to the victims has been defaced by graffiti reading “¡Viva Franco!” To which someone responded: “Fascism must not be discussed, it must be destroyed.”

“In Spain,” García Lorca once wrote, “the dead are more alive than the dead of any other country in the world.”

To date, the remains of 75 people have been recovered in Viznar. The passage of time and lack of records about the killings make identification difficult, so researchers are using bone samples to perform DNA tests in a Granada laboratory. The first results are expected this fall.

But many relatives worry it will be too late.

“Who’s responsible for the samples? Who?” Francisca Pleguezuelos Aguilar, 73, anxiously asked a perplexed forensic expert during a recent visit to the laboratory.

Pointing at a window behind which two lab assistants in white overalls were showing the DNA testing process to families, Ms. Pleguezuelos said she worried that the conservatives would block the study of the samples if they win this week’s general elections.

She wasn’t the only one afraid. “They’ll paralyze all the projects,” said María José Sánchez, a great-niece of the barmaid who was killed, her eyes swollen with tears. “The curtain is about to fall again.”

A spokesperson for the Popular Party suggested that exhumations could continue after the elections, saying that “relatives have the right to claim the bodies of their loved ones.”

But many relatives said they remembered how Mariano Rajoy, Spain’s previous conservative prime minister, boasted of having cut public funding for the 2007 memory law to zero..

The possibility of a national alliance between the conservative Popular Party and the hard-right Vox party — which polls suggest will be the only way for the right to secure a majority in Parliament — has only exacerbated the fears of victims’ families.

In recent weeks, they have been looking anxiously at local governing coalitions forged between the two parties following regional elections in May: they almost always included plans to clamp down on memory projects.

“The central government is our last bulwark, our Alamo fortress,” said Matías Alonso Blasco, who represents families in the Valencia region, where the right recently took political control. “If it falls, it’s over.”

Several representatives of Vox declined to comment for this article.

In the Valencia region, the new right-wing coalition said, “the norms that attack reconciliation in historical matters will be repealed.” Many took it as a reference to the 2017 local memory law that has helped excavate about two-thirds of the area’s 600 mass graves.

Many of the bodies were recovered from the cemetery of Paterna, a suburb of Valencia. There, some 2,200 people were shot by Franco’s firing squads against a wall that is still pockmarked with bullet holes. So numerous are the mass graves that they have been given numbers.

Standing between two wooden signs marked 100 and 101, Marilyn Ortíz Bono said the body of her grandfather had yet to be identified because the remains found in the grave where he is believed to have been buried had decayed too much.

Ms. Ortíz said that shortly after Vox gained power in the Valencia region, she sent a sample of her DNA to a state-funded laboratory, hoping to get the identification process completed before the general elections.

“I haven’t heard back from them,” she said. “I’m afraid I never will.”