U.S. Sens. Dianne Feinstein of California and Ron Wyden of Oregon share a number of bullet points on their résumés.

Both are Democrats who grew up in Northern California (Feinstein in San Francisco, Wyden in Palo Alto). Both graduated from Stanford. Both serve on the Senate Intelligence Committee.

On questions of surveillance by the federal government, however, they might as well inhabit different planets.

As revelations spill forth about how much data the government secretly gathers, Feinstein has emerged as chief defender of the national security state. Wyden remains one of its staunchest critics.

In recent years, Wyden and his soul mate on the Senate Intelligence Committee, Mark Udall, have sounded cryptic alarms about government intrusion.

"I acted in every possible way short of leaking classified information,'' he told The New York Times last week.

Meanwhile, Feinstein, the chairwoman of the committee, jumped to defend the government's secret harvesting of telephone and Internet records.

"We're always open to change, but that doesn't mean that there will be any,'' she said. In politics, that's code for sit down and shut up.

Background

Why the difference? Temperament counts. Feinstein, the daughter of a surgeon and one of the Senate's first powerful women, revels in her role as insider. The writer David Talbot once described her as having a "Big Nurse'' personality. It's not inaccurate.

Wyden, the son of a journalist, doesn't mind being a maverick. When Senator Rand Paul, R-Ky., filibustered in March over the government's rules for use of drones, Wyden joined in his protest.

Let me suggest two other contributing factors. One reflects a generational chasm. The second has to do with the searing event that provided the crucible for Feinstein's political career.

Adage says that if you want to know someone's politics, look at the newspaper headlines from the time they were 20. Feinstein, now 79, came to maturity during the Dwight Eisenhower years, a time of respect for government.

Wyden, 64, graduated from college in 1971, when Richard Nixon was president, the Vietnam War was raging, and distrust of government was soaring. I graduated that same year. It left a birthmark of skepticism toward authority.

Assassination

Later that decade, a bad one on so many counts, Feinstein became mayor of San Francisco after ex-Supervisor Dan White killed Harvey Milk and Mayor George Moscone.

That tragedy offered Feinstein a visible path to leadership but laid down its own imprint. If you think of White as an early author of terror, it's not hard to see why Feinstein fiercely defends a national security state.

That doesn't make her right. Wyden has a better purchase on the truth. But it helps explain why the two live on different planets.

Contact Scott Herhold at 408-275-0917 or sherhold@mercurynews.com. Follow him at Twitter.com/scottherhold.