Beware every single Democratic presidential candidate when it comes to the Medicare prescription drug benefit. All of them would implement a change that would ruin one of the most successful elements of the program.

Again and again on Tuesday night, as was the case in all discussions on the issue in prior debates, all the candidates agreed that “the government” should “negotiate” the prices for Medicare Part D drugs. Democrats have been pushing this idea for two decades, even before the Part D program was created in 2003 legislation. The statistics show the idea was bad then, and that the system has worked immensely better without government negotiation ever since.