Karen Bass can start packing her bags – she'll take over the Assembly's top job May 13.

The news ends uncertainty that began after she was named speaker-elect nearly two months ago and said she would work with incumbent Speaker Fabian Núñez to transition into the job.

Bass, D-Los Angeles, will be thrust immediately into what are expected to be bitter budget talks over a remaining deficit estimated to be at least $8 billion.

"Frankly, we're facing such a huge deficit that I'm not sure it mattered whether I took over now, a month ago, or two months from now," Bass said Thursday.

Gov. Arnold Schwarzenegger is expected to release his revised budget proposal in mid-May, essentially launching a partisan war.

Bass said the May 13 date was mutually agreed upon by her and Núñez, D-Los Angeles.

"I wanted it to be before budget negotiations were really hot and heavy," said Bass, 54, the first African American woman to lead a California legislative house.

Steve Maviglio, Núñez's spokesman, described the transition as "seamless."

The mid-May takeover ensures that Bass will be the clear leader, and key fundraiser, before the June 3 primary election for all 80 Assembly seats.

"She has immense talent and passion for good public policy," said Sen. Darrell Steinberg, the Sacramento Democrat who will lead the Senate next year. "I'm very excited about working with her."

Larry Gerston, political science professor at San Jose State University, said power begins to shift automatically once a speaker-elect is chosen, as Bass was on Feb. 28.

"Once that caucus vote is taken, they all line up," Gerston said.

Gale Kaufman, Núñez's strategist, said the May 13 swearing-in provides Bass with authority and a solid support system.

"Fabian isn't going anywhere, so his experience – and the leadership team's experience – will be invaluable," Kaufman said.

Bass described her new job as the "biggest challenge I've had to face in my life."

"But I'm one who loves challenges and loves new experiences," she said.