Katy Tang was driving Monday evening when she received a long-awaited telephone call. “Pull over,” the voice on the phone said.

It was sage advice from Mayor Ed Lee, who made his own sage move Tuesday when he selected Tang to succeed Carmen Chu as the Sunset district’s representative on the Board of Supervisors.

The decision percolated in Lee’s mind since Chu was selected to head the Office of Assessor-Recorder, leaving a vacancy on the board. The mayor selected Tang, 29, who has been Chu’s legislative aide for more than five years and grew up in the district, because “continuity was important for the residents and businesses of District 4,” Lee said.

In Tang, “they know they have a member of the team who represents that continuity,” said Lee, who will swear in Tang today.

Political hopefuls would be hard-pressed to find a better platform to launch a campaign than the job Tang did in Chu’s office. “She went to every meeting, she went to every event,” said longtime Sunset businessman Benny Yee, a former merchants association leader. “When people asked me who the ideal person would be, I said, ‘Katy Tang.’ She really is superb; second to none.”

Flanked by her parents, who sent her to neighborhood schools and Lowell High on The City’s west side, Tang thanked her former boss and mentor Chu – who received high marks for her attention to the district– and pledged to follow in her footsteps. Tang said she already has a focus on district issues.

“Everyone always says work is work and you should separate your work life from your personal life,” Tang said. “But for me, work is very personal.”

Tang pledged to continue Chu’s efforts of restoring neighborhood parks and schools and working on transportation in the Muni-reliant district.

The newly minted supervisor is both young and a political neophyte, but emerged as the best choice for Lee despite a push from some insiders to appoint a mother to the seat. Police Commissioner Suzy Loftus, 38, also a neighborhood native, had backing from members of the Democratic County Central Committee. Others close to Lee pushed for Malcolm Yeung, who has close ties to Chinatown leader Rose Pak

Lee was under pressure to choose wisely for this appointment after picks last year for supervisor and the City College of San Francisco board of trustees failed to win subsequent elections. The City Charter stipulates that appointees must stand for election on the next ballot, which in this case is November.

As a Mandarin speaker born in New York City who spent most of her life in the Sunset, Tang is likely a solid favorite to win election in District 4, which is estimated to be more than 50 percent Chinese and has picked a representative of Chinese descent since district elections came back in 2000.

Political watchers and Sunset residents alike could not name a likely or even possible challenger to Tang in the November election. Chu also cruised to re-election unopposed in 2010.

Chu is seen as a staunch loyalist to Lee’s tech-savvy, business-friendly agenda, and Tang has indicated that she will continue that legacy.

croberts@sfexaminer.com

Note: This story was updated Feb. 27 to correct Katy Tang’s place of birth to New York City.