The San Francisco district attorney needed support from key unions and different parts of California when she launched her first statewide campaign.

So almost 15 years ago, Kamala Harris connected with another rising star, Laphonza Butler, then the Los Angeles-based leader of the fast-growing home-care workers union. Harris wanted the local union’s backing in her bid for state attorney general.

“First, you need to walk a day in the shoes of one of our members,” Butler, now a Democratic senator from California, recalled instructing the future vice president.

Harris took her up on it. She spent an entire day witha home-care provider in Oakland, working with the elderly and disabled in their homes. She earned the endorsement of the SEIU 2015, and went on to narrowly win the 2010 election. She also forged a long-lasting bond with Butler.

Butler has known the vice president since that first campaign and supported her next two statewide campaigns, including the Senate bid in 2016 that put Harris on the national radar. She also worked as a top policy adviser on Harris’s short-lived presidential primary campaign in 2019.

Now, through a mix of happenstance and insider smarts, Butler, 45, is poised to potentially wield far more clout than Washington expected when she was sworn in last October for an interim appointment to replace the late Sen. Dianne Feinstein (D-Calif.).

Butler has impressed colleagues who appreciate her expertise in the labor movement as well as her time running Emily’s List, the political organization charged with electing female candidates who support abortion rights. She has honed what she calls the “skill of influence” in the Senate, learning what makes all 100 tick in a chamber that would be critical to a first-term agenda should Harris win in November.

Other senators, particularly Alex Padilla (D-Calif.) and Patty Murray (D-Wash.), have close ties to Harris, but they are charting long-term careers in the Senate. Not Butler, whose tenure ends whenever California officials declare a winner in the November special election.

Friends see Butler not just as a smart temporary colleague, but possibly as a long-term power broker in a potential Harris administration with the new bonds forged during her brief time in the Senate.

“You know, she’s got executive capacity, as well as legislative skills and extraordinary personal skills. So I can see her playing a very prominent role in a Harris administration. She has enormous goodwill here,” Sen. Peter Welch (D-Vt.) said.

For now, Butler is focused on two jobs: “Senate-ing” (her phrase for her unexpected stint representing 40 million Californians), and helping Harris’s latest campaign.

“I am doing everything that I can to protect the future of this country, by helping Vice President Harris become President Harris,” Butler said in a telephone interview Wednesday.

If that works out, Butler wants to play whatever role the new president would consider.

“I believe in her and her leadership, and if she felt like there was something that I could offer, I of course would have to consider it,” Butler said. “You don’t get asked to do something by the president of the United States very often.”

In a Senate still so antiquated that some newcomers do not deliver speeches their first year in office, many interim senators in recent years have left little to show for their brief tenure.

George Helmy, the new appointee to replace Sen. Bob Menendez (D-N.J.), convicted on felony charges last month in a bribery case, is not expected to do much beyond voting the party line in the less than five months he will serve.

Some might have initially seen that role for Butler, but she quickly impressed many senators. Then the June 27 debate took place, sending President Joe Biden into a political free fall within the Democratic Party.

Butler so happened to be on a three-day trip through California with Harris at that time. When she returned to Washington the next week, she delivered the Biden-Harris mantra.

“The future of our democracy is at stake. And we’ve got to get out, do the work, not take a single voter for granted,” Butler told reporters on July 2, never wavering in her support for Biden.

Now, with Harris atop the ticket, Butler’s thoughts matter even more.

When political firestorms arise — like former president Donald Trump’s appearance on July 31 before Black journalists when he questioned whether Harris was truly Black — Butler can channel Harris’s instincts in how to respond.

“Look, this is the only tool he has. He has no vision for the country,” Butler told reporters soon after Trump’s remarks.

She provided the road map for Team Harris: Punch back at Trump’s extreme remarks, then return to pocketbook issues that the swing voters consider most important and highlight the controversial ideas of Project 2025, a far-right agenda promoted by former Trump administration officials.

“We are not going to ignore it,” Butler said then of the incendiary remarks. “But we have to actually get to a place where we’re engaged on the issues that American people care about.”

Butler grew up in Magnolia, a small majority-Black town with a population of just a few thousand, 85 miles south of Mississippi’s state capital, where she attended Jackson State University. After several union-organizing jobs for nurses and janitors in places like Baltimore and Philadelphia, Butler moved to Los Angeles to run the home-care workers union.

California Gov. Gavin Newsom (D) appointed Butler to the Senate in October after Feinstein’s death, following a series of prolonged health battles. In early 2021, Newsom promised to appoint a Black woman to replace Feinstein if she ever could not finish her term, after he had just appointed Padilla, the first Latino senator from California, to replace Harris in the Senate.

By summer 2023, Feinstein had already announced she would retire and there was a full-scale campaign launched among several competitors. Newsom did not want to interrupt that race by choosing sides, leading many to think he would appoint someone who promised to serve briefly and not run a full term.

That angered some Black activists who felt it was patronizing to appoint a Black woman to serve in the job only temporarily.

When he chose Butler, Newsom won plaudits from liberal activists across California and he also gave her carte blanche to run for the seat if she wanted it.

Despite the head start that the eventual Democratic nominee, Rep. Adam Schiff, and others had, Butler analyzed the race as if she were a hardheaded political strategist again.

“Could I raise the money? Could I get the endorsements? Would I actually be able to take some endorsements from folks who were already in the race? And the answer to those questions was, yes, and absolutely,” she said.

And she talked to Harris. “Never did she tell me what to do. She doesn’t — she’s not that kind of a mentor and a friend. She is the kind of friend who talks through all of the different aspects and opportunities, the challenges, the sacrifices, the pluses and minuses,” Butler said.

Instead, with a young daughter who would be 16 at the end of a full six-year term, she and her wife decided it wasn’t the right time for elective politics.

And now, after one crazy month of July, she gets to focus again on helping Harris in the campaign of her life.

Butler has been impressed with Harris’s ability to take the already existing Biden-Harris campaign and scale it up to include several prominent veterans of previously successful presidential campaigns, something that was lacking in Harris’s bid five years ago.

“While you have people who are strategists and/or other kinds of experts, the experience of running a presidential campaign is invaluable,” she said.

Still more of an executive than a legislator, Butler has relished having a front-row seat for major legislative battles, including the border crisis and funding Ukraine’s defenses. She became a fully engaged senator without having to grind through raising tens of millions of dollars to try to win an election.

Welch, 77,reached the Senate nine months before Butler did, and only after a lengthy career that started in state politics in 1981. Despite three decades in age difference, they find themselves in a similarly junior status and often remain studiously quiet during caucus lunches.

They then find ways to buttonhole key senators to try to privately influence debates, Welch said. “She combines the capacity to be very direct and clear with an open and welcoming demeanor. She’s gifted.”

Any question about the next job, however, prompts Butler to focus on the more important job directly in front of her.

“I am resolute, in my demonstration of my commitment to the future where my daughter can believe that she can one day be president,” she said. “And I think this is our opportunity to do that.”