One Friday in early August, Nancy Pelosi and Gavin Newsom sat together in the historic governor’s mansion in Sacramento and began dialing some of the nation’s wealthiest Democrats for dollars.

Ms. Pelosi, the 85-year-old former House speaker, and Mr. Newsom, the 57-year-old governor of California, have known each other for decades. She has been his mentor, and their circles are so entwined as scions of San Francisco that their families were even blended by marriage at one point.

But this was something entirely new for them both as they raced to raise cash for a fall ballot campaign on redistricting that could shape the 2026 midterms.

Ms. Pelosi would begin with pleasantries, according to three people granted anonymity to discuss private fund-raising calls made that day. Then she would hand the phone to Mr. Newsom to close the deal. The choreography was partly borne of a mindfulness of tangled federal rules about soliciting outsized checks, and partly out of deference to Mr. Newsom.

Well, at least most of the time.

“That’s certainly not enough,” Ms. Pelosi blurted out to one potential contributor who had floated a sizable, but apparently not sizable enough, donation. Everyone burst out laughing, according to two people with knowledge of the tandem fund-raising. “I think we can do better,” she ribbed at another point.

The moment at the mansion provided a glimpse of Ms. Pelosi’s behind-the-scenes role in a redistricting push with national consequences. At President Trump’s behest, Republican-led states, starting with Texas, are moving rapidly to rip up their congressional boundaries and boost G.O.P. chances of keeping control of the House next fall. California represents Democrats’ biggest and best hope for a meaningful counteroffensive.

Mr. Newsom is asking voters to approve a ballot measure to amend the state constitution, which currently prohibits partisan gerrymandering, in order to allow for new maps that would give Democrats five additional seats — a bid to effectively cancel out Texas.

Ms. Pelosi is not the face of the redistricting fight in California. That role clearly belongs to Mr. Newsom.

Nor was Ms. Pelosi at the forefront of designing the state’s new proposed voting lines or massaging the considerable egos in the California delegation. Those tasks fell chiefly to Representative Zoe Lofgren, the state delegation chair, and Representative Pete Aguilar, the House Democratic Caucus chair.

But Ms. Pelosi has been quietly pivotal from the start.

Mr. Newsom sought her private counsel and support over the summer before plowing ahead with his redistricting measure, named Proposition 50. She was a key sounding board for Eric H. Holder, Jr., the former attorney general, as he decided to abandon his commitment to nonpartisan mapmaking. She counseled some California members of Congress whose districts were being drawn out from under them. And her early endorsement served as a permission slip for lawmakers in both Sacramento and Washington, D.C., to get on board.

Long a top party fund-raiser, Ms. Pelosi is now seen as a linchpin to finance a ballot campaign that could exceed $200 million. And she has already pushed top contributors to activate their networks with uncommon urgency.

Ms. Pelosi’s role was described in interviews with 20 lawmakers, strategists, donors and others involved in the redistricting fight, some of whom insisted on anonymity to describe private and sensitive discussions. Ms. Pelosi herself declined multiple interview requests.

“Having her imprimatur really matters,” said Representative Jared Huffman, whose new district would stretch from the Golden Gate Bridge to the border of Nevada and Oregon.

“There was a skepticism,” Mr. Huffman explained. “If Nancy wasn’t all in and ready to lean in with fund-raising and mobilization, this was going to be a super heavy lift. And so when she signaled that she was ready to do all of that — that was significant.”

Ms. Pelosi stepped down as the Democratic leader in 2022, but she continues to shape her party. And despite a growing Democratic clamor for generational change, she has not yet ruled out running again in 2026, a term that she would complete at the age of 88.

After fracturing her hip last December, Ms. Pelosi had to abandon her stilettos for sneakers. Recently she has begun to sport at least some low heels again, a symbol of something between her stubbornness and staying power.

For Republicans, Ms. Pelosi’s involvement provides a ready-made foil.

“She has a known history of opposing independent redistricting and placing party loyalty ahead of public interest,” said Jessica Millan Patterson, a former chair of the California Republican Party leading a “No on 50” campaign.

Ms. Lofgren, one of Ms. Pelosi’s closest allies, said that the former speaker sees many of her accomplishments at risk of being undone by the Trump administration, and that the ballot measure is the best way to fight back.

“That’s what is fueling her,” Ms. Lofgren said.

Redistricting is ‘in her blood’

Nearly two decades after she broke barriers as the first woman speaker of the House, the redistricting fight has emerged as something of a legacy project for Ms. Pelosi. But in many ways gerrymandering has been part of her political story from the very beginning.

The San Francisco congressional seat she occupies was previously held by Phillip Burton, a Democrat who was obsessive about drawing partisan districts to gain every advantage. He famously called the contorted California map that he created in 1981 “my contribution to modern art.”

The state party chairwoman at the time was an ambitious 41-year-old by the name of Nancy Pelosi.

Perhaps the most gerrymandered district that Mr. Burton designed wound up inadvertently smoothing Ms. Pelosi’s own rise. He had set out to create a safer seat for his brother by giving up some of the most liberal bastions from his own San Francisco district, including the Haight-Ashbury and parts of the Castro.

Six years later, those changes would prove crucial for Ms. Pelosi in her first congressional run, when she narrowly bested a more progressive challengerby less than 4,000 votes.

“She almost certainly would not have prevailed” without that remapping, said Marc Sandalow, a Pelosi biographer.

She would never face a close race again.

By 2001, Ms. Pelosi was at the center of another redistricting battle.

She was a rising power in the House, campaigning to become the whip and intimately involved in the state’s mapmaking. “Essential with exclamation point,” recalled Robert Hertzberg, who oversaw 2001 drawing as California Assembly speaker. “We listened to her.”

At one point, the lone California House Democrat not backing Ms. Pelosi in the whip race publicly accused her of trying to erase her seat as payback. Ms. Pelosi waved away the accusations as “a waste of my time.”

The map she blessed was a bipartisan gerrymander in which incumbent Democrats and Republicans alike were protected. It was so effective only a single seat would change party hands for the entire decade. And California’s safe Democratic delegation would prove a loyal base of Ms. Pelosi’s support.

“Redistricting has always been in her blood,” said Brian Wolff, who served as one of Ms. Pelosi’s top lieutenants in the late 1990s and early 2000s as she rose to power in the House. “I don’t think it’s just part of her history, it’s part of her being.”

But a backlash was brewing to a system that insulated politicians so thoroughly from public opinion.

In 2005, Arnold Schwarzenegger, then the Republican governor, promoted a ballot measure to strip legislators of their mapmaking powers — a measure Ms. Pelosi helped to defeat. But he succeeded in 2010 in convincing voters to put an independent commission in charge of congressional mapmaking.

That year, Mr. Newsom broke with Ms. Pelosi by opposing an effort she backed to repeal the commission.

He still remembers getting an earful from her.

“Those,” he said with a laugh, “are memorable phone calls.”

For her part, Ms. Pelosi had long argued she wasn’t against independent commissions, but that she simply didn’t want Democrats to cede power unilaterally. In 2021, she made an election reform package, which called for independent redistricting commissions nationwide, the first bill introduced under President Joseph R. Biden Jr. It stalled in the Senate.

‘Queen bee’ goes to work

This summer, the idea of California drawing a retaliatory map to counter Texas was still just that — an idea — when Ms. Pelosi sent Mr. Newsom a text message suggesting that he talk with Ms. Lofgren.

“I need to know where you guys are on this,” Mr. Newsom said he told Ms. Lofgren.

The answer: California’s House Democrats were surprised that he was serious. Asking California voters to rewrite the state constitution even on a temporary basis had begun as something closer to a bluff to discourage Texas Republicans.

“Our first goal was to make them stop, but it didn’t work,” Ms. Lofgren said in an interview. “So then we moved from threat to action.”

In private meetings with the state’s delegation, Ms. Pelosi’s early support of redrawing the maps had proved crucial in uniting the state’s Democratic members of Congress, according to multiple attendees. “Without any brow beating, every member agreed,” Ms. Lofgren said.

Next came selling state legislators in Sacramento. Ms. Pelosi was involved in that, too.

As Democratic Assembly members lunched on barbecue and mac and cheese at the State Capitol in mid-August, Ms. Pelosi, Ms. Lofgren and Hakeem Jeffries, the Democratic leader, beamed in by video.

“She gave a rallying cry about what’s at stake and why we needed to do it,” Assemblywoman Buffy Wicks said of Ms. Pelosi’s remarks. “She is the queen bee for California.”

The plan would pass days later with little Democratic dissent.

All that was left was getting voter approval. And raising an estimated $100 million — a blistering pace of more than $1 million a day that Ms. Pelosi is seen as crucial to achieving.

“There’s a lot at stake for the country; this is not just about California,” Mr. Newsom said in an interview. “It’s about our democracy. It’s about control of Congress. It’s about the rigging of an election. We need national support and Pelosi, as the former speaker, gets that.”

Ms. Pelosi has already been working some big party donors, including Ron Conway, an influential tech leader. Last month, the same day she spoke with California legislators, she attended a $2 million fund-raiser at a waterfront home on Martha’s Vineyard with former President Barack Obama for the National Democratic Redistricting Committee, which is engaged in the redistricting fight nationally.

“This isn’t about partisanship,” she told attendees. “This is about doing the right thing.”

She is also publicly making her case.

Next month, when ballots and election guidebooks arrive by mail for millions of California voters, there will be three people carefully selected to promote “yes.”

The first is Mr. Newsom. The second is California’s senior senator, Alex Padilla. But the final name is Ms. Pelosi.