Public agencies can't use public dollars to campaign for ballot measures. Just imagine if they could: A school district puts a bond measure on the ballot, then uses some of the voters' tax money to send out slick mailers to persuade those same voters to adopt the measure. Unhappy voters could organize an opposition campaign, but even as they pay out of one pocket to defeat the measure, the district reaches into their other pocket -- their taxpaying pocket -- to pass it. At some point the district looks less like a public agency and more like a racket.
Agencies need not remain silent while others speak. That same district may legally use public resources to let voters know the probable consequences of the ballot measure. It can, for example, post on its website what services it plans to add if the measure passes, or what it will have to cut if it doesn't. Advocacy, no; analysis, yes.
Some agencies play too close to the line. Consider the Los Angeles Unified School District's publicly funded campaign for -- oops, make that campaign about -- Measure Q on last November's ballot. A mailer called on voters to "Learn more about Measure Q and how it makes our schools safer" and to "Remember to vote on Q Nov. 4th." Not "vote for Q," mind you. But even without the magic word "for," the school district made it quite clear what it wanted voters to do.