Tevi Troy shares with Wall Street Journal readers his analysis of Democrats’ reliance on a tried-and-true campaign tactic involving Medicare.

The first GOP debate hasn’t even taken place, but one of the Republican candidates is already under attack on Medicare. In New Hampshire on July 22, Jeb Bush said he wanted to “phase out” traditional Medicare to build a more efficient, market-based system, focused on patients. It didn’t take long for Democrats to pounce. MSNBC and the liberal blogs sensationalized the comment. The Democratic National Committee’s press secretary, Holly Shulman, claimed that under a Bush presidency working Americans “won’t have the same health benefits that seniors rely on.”

That Democrats are once again deploying the Mediscare tactic shouldn’t come as a surprise to Mr. Bush or any of the other 2016 GOP hopefuls. These campaigns of accusation and obfuscation have a long political history, going back at least as far as President Jimmy Carter’s losing run for re-election against Ronald Reagan in 1980.

Mr. Carter repeatedly accused Reagan of opposing the creation of Medicare, including a strident salvo used in his only debate against Reagan. In response to Mr. Carter’s Medicare accusation, Reagan issued his famous “there you go again” retort, which helped sink the Carter campaign.

Yet most people forget that Reagan went on to explain that he was not opposed to “the principle of providing care” for seniors. “When I opposed Medicare,” he said, “there was another piece of legislation meeting the same problem before the Congress. I happened to favor the other piece of legislation and thought that it would be better for the senior citizens and provide better care than the one that was finally passed.”

Since then the attacks on Republicans over Medicare have grown in intensity as the program has expanded. Between 1975 and 1990, Medicare spending increased at 2.4 times the inflation rate. The program that was first slated to cost $12 billion in 1990 actually grew to $110 billion. By 2014, the program cost $511 billion. With increased spending and dependence, the attacks grew fiercer.