Senator Dianne Feinstein’s vote in favor of the new surveillance law is a disgrace.

She has always been somewhat chilly toward civil liberties, but I’ve understood her positions from the frame of reference of her background in law enforcement. I also understood politicians’ fear of being labeled soft of terrorism in the immediate aftermath of the 2001 attacks. The latter was a contemptible abandonment of principle when it came to supporting drastic new police powers, but it’s sadly foolish to expect politicians to defend liberty in difficult times.

This vote, however, compounds the damage.

Rather than claiming they’ve preserved checks and balances, Sen. Feinstein and the other Democrats who supported this breathtaking expansion of government surveillance should at least acknowledge what they have done. They have given the most untrustworthy government in recent memory an essentially untrammeled ability to spy on Americans.

The law’s vague language that gives the administration — which has demonstrated again and again that doesn’t care much about law in the first place — ample room to widen its surveillance nets to capture anyone’s communications for any reason and with little or no oversight. The 6-month re-examination is meaningless given Congress’ quisling history in such matters, and so are the alleged watchdog measures.

In important ways, we will be less secure as a result of this law. The inevitable abuses, when we eventually learn about them, will lead Americans to have even less trust in our government. Moreover, a surveillance state creates a self-censoring, somewhat paranoid sense of being watched that inevitably inhibits the kind of robust free expression and creativity that a self-governing people needs. If China’s attempt to combine a repressive political system with quasi-free enterprise is Sen. Feinstein’s model for a future America, she is voting appropriately.

Yes, there are potential security risks in not being able to spy on everyone and anyone without serious oversight. But America’s meaning is that we take some risks in order to be more free, because liberty’s benefits outweigh the costs. When we trust in liberty, we end up stronger, not weaker.

I love my country, and I love our Constitution. No one, least of all me, doubts that Sen. Feinstein also loves her country. But she has apparently forgotten her oath of office, in which she swore to “support and defend the Constitution of the United States.”

I don’t know whether her vote is the act of a political coward or a politician’s conclusion that Bill of Rights is an outmoded ideal. I suspect it’s a combination.

But I do know this: Sen. Feinstein earned my vote in the past with positions that were, while imperfect from my viewpoint, at least better than her opponents’. With this betrayal of liberty and the Constitution, she has lost more than my support as a voter. She has lost my respect.