The three rivals for the Democratic presidential nomination showed enough sense of responsibility in their debate on Saturday to freely discuss the nation’s epidemic of gun violence. Unfortunately, this was only half the debate voters deserve. The Republican candidates are callously ducking the issue. Among the recent casualties of such silence was a bill in Congress that would have lifted a ban on basic federal research into gun violence and its toll on public health.

For nearly two decades, Congress has banned needed research on gun violence by the Centers for Disease Control and Prevention. Last week, Congress, doing the bidding of the gun industry, quietly killed a provision in the omnibus spending bill that would have reversed that ban.

In so doing, it left intact an anti-science smoke screen that has helped the industry and its lobbyists deny and dispute the facts of the gun violence that takes more than 30,000 lives a year.

Imagine if the tobacco industry had been similarly favored by Congress with a ban on federal research about cigarette deaths. Imagine, too, if the auto industry had such a shield during the years when the government successfully fought unsafe cars in the cause of public health.