And now the two of them are at the center of what has become the critical battle in Mr. Brown’s first few months on the job, as he tries to push through a budget that would almost certainly define much of his remaining years here. And for all of Mr. Brown’s knowledge and self-assurance, it is this unlikely budget director — a Republican appointee — to whom the governor keeps turning to help him navigate this treacherous terrain.

When Darrell Steinberg, the State Senate president and a Democrat, was at a budget hearing about a state ballot initiative that changed the way local government operates, he asked the governor, “Can you give us a brief history lesson on that?”

Mr. Brown paused. “I’m not sure about that,” he said, gesturing Ms. Matosantos over. “Ana, why don’t you try?”

Without hesitating, she explained how the state made up for services that local governments could not afford.
Months later, Bill Emmerson, a Republican state senator, asked for similar information in a private meeting. Ms. Matosantos ticked off the information without looking at any notes, convincing Mr. Emmerson that an inflexible spending cap would not work. A few weeks later, Mr. Emmerson could not remember the details himself. But he was certain that Ms. Matosantos had given them the right guidance.

“She’s nothing but a straight shooter, doesn’t play any games,” he said.

Like the governor, Ms. Matosantos is in her second tour of duty. She was appointed director of the California Department of Finance by Gov. Arnold Schwarzenegger in 2009. And when it came time for Mr. Brown to look for the person who would help him close the state’s crippling $26 billion budget gap, advisers from all corners of the Capitol urged him to reappoint Ms. Matosantos.

“She’s often the smartest person in the room: the one who knows how everything works,” said Mr. Emmerson, who added that keeping Ms. Matosantos was “the smartest thing Brown has done so far.”
While the Legislature has moved forward in approving more than $11 billion in cuts, parallel negotiations to put a tax extension up for a statewide vote have sputtered and stalled. Now Ms. Matosantos is going through marathon meetings with Mr. Brown, as well as painstaking, occasionally painful sessions with Senate Republicans, whose votes are needed to get the tax initiative on a June ballot. Without those taxes, Mr. Brown has said, the cuts to the state’s budget will need to be even more draconian.

Ms. Matosantos’s days are typically filled with meetings explaining the budget or working with her assistants to analyze the state’s cash flow. But those meetings are often shelved when the governor calls for an urgent talk; it might be another session of hammering out possible changes to public employee pensions or considering another way to structure local government services.

So on a recent Tuesday, Ms. Matosantos walked back into her office with a sandwich and two sodas, her fuel of choice for marathon budget sessions. She had hardly set down her lunch when her secretary said,

“The governor wants to see you as soon as possible.”

The sentence was not even finished before Ms. Matosantos began walking out the door.

“Do you know what it’s about?” she asked, knowing the answer would be no. “I’ll be back.”

Her secretary smiled and said to nobody in particular, “Yeah, I’ve heard that before.”

Two hours later, the sandwich was still in its bag and the cans of Diet Coke were still unopened.

“It gets to the point where this is the only thing you can think about,” Ms. Matosantos said in an interview in her office, where copies of state budgets line the walls. “I started this job when we were at the worst point since the Great Depression.”

This was never the career she imagined growing up in Puerto Rico, the daughter of a high school administrator and a businessman. She expected to go to law school, but after graduating from Stanford with a degree in political science and feminist studies, she applied for a fellowship in Sacramento and quickly moved through the Capitol.

Ms. Matosantos seems unconcerned about her status as a first in so many categories — in addition to being the youngest, she is the first Latina and the first openly gay person to hold the job — and likes to keep her matter-of-fact tone on any topic. “At the end of the day, what matters is the numbers: this all has to add up and make sense.”

Government is so ingrained in Ms. Matosantos’s life that she met her partner though her state work. When Ms. Matosantos was working on health care issues, she met Sally Espinoza, who was also working on similar issues as a staff member for a Democratic senator. The two have been together for nearly a decade and bought a house a few miles from the Statehouse.

With same-sex marriage still tied up in courts here, the couple set a date for a commitment ceremony last fall but nearly missed it when budget negotiations dragged through October. The ceremony went forward; the budget had passed just days earlier.

During one battle over health care regulations several years ago, Ms. Matosantos and her Republican counterpart in the Senate minority office had to write two different versions of the same bill. But the Republicans were short-staffed, and when Michael Genest, the chief of staff, mentioned that he was overwhelmed, Ms. Matosantos volunteered to help.

“We were in the legislative library and she just turns and says, ‘Well, don’t worry, I can do your bill for you,’ ” Mr. Genest said. “And within a day she had drafted Republican and Democratic versions of the bill — both exactly looking like what the leaders wanted.”

A few years later, Mr. Genest was Mr. Schwarzenegger’s budget director and hired Ms. Matosantos as his deputy.

“I knew she just wants to move the process forward and is very smart about how to do that,” Mr. Genest said.

But working countless hours to cut the same programs that Ms. Matosantos helped create at the beginning of her career is not easy. On more than one occasion, she seriously discussed the possibility of leaving her position rather than making another round of deep service cuts to the disabled.

“But really, there is no choice,” Mr. Genest said. “If she doesn’t do it the right way, it means somebody else is going to have to do it eventually.”

Adam Nagourney contributed reporting.