Kamala Harris learned a lesson about the border early in her career. It’s paying off now.

SACRAMENTO, Calif. — With her recent support for stricter border security, Vice President Kamala Harris is borrowing from a familiar playbook: her own.

Harris’ pledge to fight for border security traces its roots to her campaign for California attorney general in 2010, when she narrowly defeated a Republican opponent who had the support of police chiefs and prosecutors across the state.

Harris, a former prosecutor herself, decided to embrace a tough approach to the transnational gangs that smuggle drugs and people across the U.S.-Mexico border. She expanded a task force focused on transnational crime — during the Great Recession, when the state was cutting its budget and programs — and promoted greater intelligence sharing with Mexican authorities, which officials say led to arrests years later.

Her focus on this issue was not unique for a border state attorney general, but it marked a break from the reformist profile she had built earlier in her career. It gave her common cause with law enforcement agencies and others who saw her as a liberal from the safe city of San Francisco.

“She assembled a team within the Justice Department that had a lot of credibility with law enforcement and she took on the people, the police unions and others who had opposed her in the race,” said Brian Brokaw, a Democratic strategist who managed her campaign.

Those efforts paid off during her 2014 reelection campaign and her 2016 run for the U.S. Senate, when she garnered the support of Republican district attorneys en route to landslide victories. She’s now drawing on that chapter of her career as she seeks to undermine former President Donald Trump’s efforts to portray her as soft on border enforcement, an issue that has resonated with voters over the past year as record numbers of migrants have been apprehended trying to enter the U.S.

Harris’ support for gang-busting efforts was “huge” in winning support from law enforcement, said Mike Ramos, a former Republican San Bernardino County district attorney who endorsed Harris in 2014 after remaining neutral in her 2010 race. He is now no longer affiliated with either party.

“Once they started looking at what she was doing and they appointed a number of people to her Justice Department who were former law enforcement officers, police officers, former sheriffs, etc., they began to realize that she had an agenda that was focused on public safety,” Ramos said.

Transnational crime was a logical step for Harris, who as a young prosecutor in Oakland and San Francisco handled cases involving human trafficking, sexual abuse and other violent crimes aggravated by transnational gangs.

The theme was not a focal point for her Democratic predecessors at the California Department of Justice, including former Gov. Jerry Brown, but was a fixture of her speeches as attorney general, when she frequently referred to the tunnels used by gangs to smuggle people and drugs into the U.S.

“As Attorney General, I will lead a renewed effort to combat gangs and organized crime,” she said in her 2011 inauguration speech. “Simply put, organized criminal gangs pose the greatest challenge to public safety in California, and working with our federal and local law enforcement partners to combat the gang problem will be a key focus of our work.”

After taking office, Harris began expanding the scope of the Justice Department’s task forces to investigate organizations that smuggled people, drugs and money from Mexico into California.

That effort was hampered by a tough economy. During her first year, the state legislature and governor slashed the budget of her Division of Law Enforcement by $72 million as she navigated a financial crisis. As part of the cuts, the DOJ’s Bureau of Narcotic Enforcement was closed the following year, with parts of it absorbed into another program.

“When that was closed, we lost a lot of the capacity that we had to take down large transnational organized crime groups in the state of California, and they never recovered from that,” said Mike Sena, executive director of the Northern California High Intensity Drug Trafficking Area, who previously worked in the state Department of Justice.

Harris cut 32 of the 51 task forces within the department’s Division of Law Enforcement as part of state budget cuts. But she kept one focused on gangs and added staff to it later in 2014. She also added officers to her office in Imperial County — which borders Mexico — to focus on breaking up transnational gangs.

“She comes from a border state and works with law enforcement on these issues,” said Nevada Sen. Catherine Cortez Masto, a Democrat who worked with Harris as her state’s attorney general in the 2010s. “The San Ysidro Port of Entry in Southern California is one of the busiest. She knows it well. She’s not new to protecting our communities from this fight.”

Harris’ office released a report titled “Gangs Beyond Borders” in 2014, a month after the arrest of former Sinaloa cartel leader Joaquín “El Chapo” Guzmán. It warned that groups in Mexico, Asia and Central America — where the notoriously violent MS-13 has its roots — had teamed up with street and prison gangs in California to control trafficking routes.

That same year, Harris led a delegation of attorneys general to meet with their Mexican counterparts to discuss cooperation on transnational crime. The officials discussed how to better share tips about criminal activity and to crack down on money laundering that fueled gang violence, said former New Mexico Attorney General Gary King, who was there.

“California’s interest in transnational crime really increased when Kamala became attorney general,” said King, a Democrat who served from 2007 to 2015.

Working with Mexican leaders and law enforcement gave Harris and her colleagues the chance to conduct diplomacy on a hot-button federal issue from their state office positions amid intense media attention over gang violence and human trafficking, and because drug traffickers had apparently realized that reaching an economy as large as California’s was extremely profitable.

Attorneys who worked with Harris at the Justice Department also credit those meetings with the fact that Mexican authorities sent more tips to intelligence agencies in California in the years that followed.

“One of the things we saw right away was greater intelligence sharing from Mexican authorities to our agencies,” said Jeff Tsai, a former special assistant attorney general under Harris. “At the operational level, open communication helped facilitate exactly the kind of coordination that she had hoped to achieve.”

There were limits to Harris’s achievements in California. Her efforts to change state laws on border issues were largely unsuccessful. As attorney general, she sponsored a bill that would have allowed prosecutors to freeze the assets of transnational gang members before bringing charges against them and another bill that would have allowed law enforcement to wiretap criminal organizations as part of money-laundering investigations.

Both bills were passed by Democrats but defeated by a Democratic-majority Senate committee, opposed by the ACLU. The ACLU warned that the expanded government power would violate citizens’ rights to privacy and due process.

Harris didn’t focus on the transnational approach to gangs during her last presidential campaign, where she ran against her fellow party members. But since President Joe Biden dropped out of the race, it has become a major theme in her ads and speeches.

“I’ve gone after transnational gangs, drug cartels, human traffickers who came into our country illegally. I’ve prosecuted them in case after case,” she said at a campaign rally in Nevada. “Donald Trump, on the other hand, has talked a lot about securing our border, but he doesn’t do it.”

Trump, whose hostility to illegal immigration is a central pillar of his political identity, has tried to portray the vice president as a failed “border czar” who only recently approved restrictions that would make it harder for people to seek asylum.

Her campaign is drawing attention to the more progressive border policies she pursued in the Senate before becoming vice president, when she broke with her party colleagues and refused to deny funding for the border wall, arguing that unauthorized migrants should not be prosecuted.

Clips have been shared of Harris expressing support for closing immigration detention centers and stressing that she agreed with fellow Democrats during her first presidential campaign that crossing the border without authorization should not be considered a criminal offense.

She has since reversed her position on illegal border crossings and supports Biden’s border security package, which died in the Senate due to opposition from Trump.

The Harris and Trump campaigns did not respond to requests for comment.

King, the former New Mexico attorney general who traveled to Mexico with Harris in 2014, argues that the federal government fails to understand the real problem at the border.

“I hope that Kamala, because of her experience as a prosecutor, will really better understand that this is about fighting crime at the border,” King said. “It’s not just about telling everyone in the world they can’t come.”

Christopher Cadelago contributed to this report.