Sandie Arnott, San Mateo County deputy treasurer, was elected Tuesday to the post of county treasurer-tax collector.
She received 51 percent of the vote, defeating Dave Mandelkern 63,293 to 60,793.
Mr. Mandelkern is a former Silicon Valley entrepreneur and board member for the community college district.
Ms. Arnott is an 18-year veteran of county government.
This was a runoff election: They finished in the top two positions in a June election, but neither received more than 50 percent of the vote.
The treasurer-tax collector directs a public agency investment portfolio of some $2.4 billion.
The county's portfolio lost $155 million in September 2008 in the bankruptcy of Lehman Brothers investment bank, with a resulting loss of $6.5 million for the local high school district and $3.5 million for the elementary school district in Menlo Park.
Ms. Arnott told The Almanac in May that she supports tighter investment policies and that the risk is too great for school districts to be making independent investment decisions for their operating funds.
As for how to invest the 20 percent of the portfolio not required to be in government securities, she supports the notion seeking outside advice.
Finding an investment adviser, she said, should be done via a request-for-proposal process. Qualifications would include past performance, references, ability to match the specifications of the RFP, availability and what the candidate would charge the county for his or her services.
In the run up to the election, Ms. Arnott also proposed improving regular communication with school districts, special districts and taxpayers, and cutting treasury office costs by moving the North County offices out of a rented building and into a county-owned one.