I spent much of Thursday calling the offices of the four Democrats with one question: Why? Why had they voted against universal background checks? Begich’s office put out a statement claiming that universal background checks “do not reflect Alaska values.” How so? His office wouldn’t say. Although Heitkamp issued a press release boasting of protecting “the Second Amendment rights of North Dakotans,” calls to her office produced only busy signals. The phone in Baucus’s office rang and rang and rang. Nobody answered.

Of course, we all know the reason: The four Democrats — along with many Republicans — quake in fear of the National Rifle Association. In 1994, Baucus voted in favor of the assault rifle ban — and then nearly lost his re-election bid. He never again stood up to the N.R.A. Yes, his phones were undoubtedly jammed this week. Still, it seemed to me that his unanswered phone was a potent symbol. I could almost picture him cowering in his office, waiting for us to stop asking why he sold the country down the river.

I loathe single-issue politics, but maybe this is what it has come to. Maybe it is going to take senators like Max Baucus losing their jobs because they wouldn’t stand up to the N.R.A. Maybe it is going to require the majority of Americans who support sensible gun laws to turn themselves into an avenging political force. I wish it weren’t so, but nothing else seems to move them — not even the sight of 20 slaughtered children in Connecticut.