The county's voters promoted Ms. Arnott on Nov. 2 with 51 percent of the vote, a narrow victory with 63,293 votes to 60,793 for her opponent, former Silicon Valley entrepreneur and board member for the community college district Dave Mandelkern.
Ms. Arnott is an 18-year veteran of county government. This was a runoff election: Ms. Arnott and Mr. Mandelkern finished one-two 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 Menlo Park City School District.
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 of seeking outside advice.
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.