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

SACRAMENTO, California — With her recent support for tougher border enforcement, Vice President Kamala Harris is borrowing from a familiar playbook: her own.

Harris’ vow to fight for border security has roots in her run for California attorney general in 2010, when she barely defeated a Republican opponent who had support across the state from police chiefs and prosecutors.

Harris, a former prosecutor herself, decided to embrace a crackdown on the transnational gangs that smuggle drugs and people across the U.S.-Mexico border. She expanded a task force devoted to cross-border criminality — during the Great Recession, when the state was cutting its budget and eliminating programs — and fostered greater intelligence sharing with Mexican authorities that officials said yielded arrests years later.

Her focus on the issue wasn’t unique for a border-state attorney general, but it marked a departure from the reform-minded profile she’d built earlier in her career and gave her common cause with law enforcement groups and others who had seen her as a liberal from the sanctuary city of San Francisco.

“She brought on a team inside the Department of Justice that had a lot of very strong street cred from law enforcement, and she engaged the very people and law enforcement unions and others that had opposed her in the race,” said Brian Brokaw, a Democratic strategist who ran her campaign.

Those efforts paid off during her 2014 reelection bid and her 2016 election to the U.S. Senate, when she scored endorsements from Republican district attorneys en route to blowout wins. She is now drawing upon that chapter of her career as she tries 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 a record number of migrants have been apprehended trying to enter the U.S.

Harris’ support for gang-busting efforts was “huge” in winning law enforcement support, said Mike Ramos, a former Republican district attorney of San Bernardino County who endorsed Harris in 2014 after remaining neutral in her 2010 race. He is now unaffiliated with either party.

“When they started to take a look at some of what she was doing, and put in place some folks in her Department of Justice that were former law enforcement, police, ex sheriffs, etc., they started to realize that she had an agenda that was pro-public safety,” Ramos said.

Cross-border crime was a natural fit for Harris, who as a young prosecutor in Oakland and San Francisco worked cases on human trafficking, sexual abuse and other violent crimes worsened by transnational gangs.

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

“As attorney general, I am going to lead a renewed collaborative effort against gangs and organized crime,” she said in her 2011 inaugural address. “Put simply, organized criminal gangs represent the number one public safety challenge facing California, and collaborating with our federal and local law enforcement partners to fight the gang problem will be a major focus of our work.”

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

That effort was hampered by a tough economy. During her first year, the state Legislature and governor cut her Division of Law Enforcement’s budget by $72 million as they navigated a fiscal crisis. As part of the belt-tightening, the DOJ’s Bureau of Narcotic Enforcement closed the following year, with parts of it being absorbed into another program.

“When that was shut down, we lost a lot of the capacity we had to level major transnational organized crime groups throughout the state of California, and they have never recovered from that,” said Mike Sena, executive director of the Northern California High Intensity Drug Trafficking Area, who previously worked at the state DOJ.

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

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

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

That same year, Harris led a delegation of state attorneys general to meet with their Mexican counterparts to discuss collaboration on cross-border crime. The officials discussed how to better share tips on criminal activity and interdict money laundering that was enabling gang violence, said former New Mexico Attorney General Gary King, who was there.

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

The cooperation with Mexican leaders and police gave Harris and her counterparts the chance to engage in diplomacy on a hot-button federal issue from the perch of state offices. That came amid intense media coverage of gang violence and human trafficking and as narco traffickers had apparently realized that reaching an economy as large as California’s was particularly profitable .

Attorneys who worked with Harris at the DOJ also credit those meetings for Mexican authorities sending more tips to California intelligence officials in the years after.

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

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

Both were carried by Democrats but failed in a Democratic-majority state Senate committee under opposition from the ACLU — which warned that people’s rights to privacy and due process would be violated under the expanded government power.

Harris did not highlight the cross-border gang crackdown in her last presidential run, when facing off against fellow Democrats, but it has been a major theme in her ads and speeches since President Joe Biden withdrew from the race.

“I went after transnational gangs, drug cartels and human traffickers that came into our country illegally. I prosecuted them in case after case,” she said at a campaign rally in Nevada. “Donald Trump, on the other hand, has been talking a big game about securing our border, but he does not walk the walk.”

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

His campaign is drawing attention to more progressive border policies she adopted in the Senate before becoming vice president, when she broke with fellow Democrats in rejecting border wall funding and said migrants crossing the border without authorization shouldn’t be subjected to criminal penalties.

It has shared clips of Harris supporting the closure of migrant detention centers and underscored 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 revised her position on illegal crossings and supported Biden’s border security package, which died in the Senate because of opposition from Trump .

The Harris and Trump campaigns did not return requests for comment.

King, the former New Mexico attorney general who traveled with Harris to Mexico in 2014, argues the federal government has failed to grasp the true problem at the border.

“I hope that Kamala, because of her experience as a state prosecutor, might really do a much better job of recognizing that this is about fighting crime on the border,” King said. “It's not just about telling everybody in the world that they can't come.”

Christopher Cadelago contributed to this report.