Kamala Harris highlighted her tough-on-migration stance during a long-anticipated trip Friday to the U.S.-Mexico border in Arizona, aiming to cover off a political vulnerability and rebut Donald Trump’s core campaign message that Democrats are soft on immigration enforcement.

"The United States is a sovereign nation, and I believe we have a duty to set rules at our border and to enforce them, and I take that responsibility very seriously," Harris said in Douglas, Arizona, Friday evening after visiting the border.

Her message reflects a broader turn on immigration that reflects a changing national mood, foreshadowing a new landscape in the coming years where imposing tougher border controls will likely be the focal point regardless of which party wins the 2024 elections.

“The priorities have to be getting the border under control. The numbers are very low right now, but you can’t guarantee that that will remain the case. You also can’t be assured that the courts won’t ultimately strike down the executive orders that the administration has taken,” Sen. Chris Murphy, D-Conn., the party's chief negotiator on a major border security package earlier this year, told NBC News in an interview. “I think our ability to get other reforms into law is made easier by putting a priority on border security.”

Harris’ pitch completes a turnaround from 2019, when she took more left-leaning positions as a presidential candidate including by backing a call to reduce illegal border crossings to a civil — not criminal — violation and by objecting to Obama-era deportations.

On Friday, Harris highlighted a different side of herself: the tough prosecutor who took on international gangs and organized crime as the top law enforcement officer of California.

"The issue of border security is not a new issue to me. I was attorney general of a border state for two terms. I saw the violence and chaos that transnational criminal organizations cause and the heartbreak and loss from the spread of their illicit drugs," Harris said, adding that going after such gangs would be a priority if she is elected president.

She also emphasized that the U.S. "has been enriched by generations of people who have come from every corner of the world to contribute to our country and to become part of the American story. And so we must reform our immigration system to ensure that it works in an orderly way, that it is humane and that makes our country stronger."

Harris’ immediate goal is to signal to moderate voters that she will be an aggressive enforcer of the law and keep migration in check.

After struggling on the issue, Democrats have finally found what they believe is a winning message: Reminding voters that former President Trump pressured Republicans to kill a bipartisan bill that would impose tougher border controls and make it harder to get asylum.

Harris said that, unlike Trump, she would embrace bipartisan solutions “because I know, transnational gangs coming across the border, trafficking in guns, drugs and human beings could care less who somebody voted for in the last election.”

Trump still leads on handling border — but by less

The GOP advantage has narrowed since it blocked the bill in May.

In January, NBC News polling found that Trump held a 35-point advantage over President Joe Biden among voters asked who they trust more on “securing the border and controlling immigration,” In a new NBC News poll this month, Trump led Harris by 21 points. The poll found a stark gender divide: Trump led Harris on the border question by 41 points among men, by 52 points among white men and by 13 points among non-white men.

“The Republican political advantage on the issue of the border has shrunk because their position has been exposed. They don’t want to solve the problem, they just want to complain about the problem, and their failure to support the bipartisan border bill is ultimately hurting them,” said Murphy, who negotiated the bill with Sens. James Lankford, R-Okla., and Kyrsten Sinema, I-Ariz.

“I’m proud that Democrats, led by the Vice President, are finally talking about border security,” he said. “Americans care about this issue, and they want a party that’s going to do something about it, not just talk about it, and Democrats right now are the only party that have a plan to fix the border. Republicans don’t have a plan.”

Harris has said she would bring back that bill and push to pass it if she’s elected president.

"I won’t only bring back the border security bill that Donald Trump tanked, I will do more to secure our border to reduce illegal border crossings," she said Friday. "I will take further action to keep the border closed between ports of entry, those who cross our borders unlawfully will be apprehended and removed and barred from reentering for five years."

But Lankford said that reviving this year's border security deal s not so simple and accused Harris of being absent on the issue.

“She also said that she and Joe worked on it together with conservatives, and she was never in a single one of the negotiations,” Lankford said in an interview. “Four months of negotiations — she or her staff were never in a single negotiation.”

“Now she wants to bring it up next year. Obviously, there are parts that expire, like the border wall money,” said Lankford, the top Republican on a key Senate border subcommittee. “No bill you can just pick up and just move to another year, because it just doesn’t work that way. I think she knows that. It’s a good talking point, but mechanically, that’s not actually true.”

Harris campaign spokespeople didn't immediately comment on Lankford's assertion.

Key Democrat says border comes first

The changing politics will impact immigration policy regardless of the outcome of the election. Trump is promising mass deportations of millions of people in the U.S. illegally if he’s elected. Harris is proposing to balance tougher enforcement with creating new legal pathways for people to become Americans.

Democratic hopes of granting permanent residency to the millions of people in the U.S. illegally have all but faded, after failing under several Democratic trifectas over the last decade and a half. Harris continues to call for pathways to legal status for at least some immigrants, but her campaign declined to say when asked if she wants to normalize the status of all the estimated 11 million undocumented people in the U.S., or a smaller population like young “Dreamers” brought to the country as children.

Rep. Nanette Barragán, D-Calif., the chair of the Congressional Hispanic Caucus, noted that this year's border bill, which members of the CHC saw as far too generous to the right, was negotiated because Republicans were holding Ukraine funding “hostage.”

“There’s no way to know if the border bill is going to come back, right? If it were to come back, I hope that there’s going to be a conversation with the Congressional Hispanic Caucus on that bill,” she said, arguing that it could use revision. “That’s really a border bill. It’s not, in my opinion, an immigration bill. I would like to see more. I would like to see pathways to citizenship added in there where there’s real negotiation.”

But Murphy said the legalization component will have to take a backseat to enforcement in the near future.

“I certainly support a path to citizenship, but I think you’ve got to probably first show the American that you’re committed to a rules-based immigration system,” Murphy said. “And that will make it easier to find a pathway for folks who are living in the shadows of the economy.”