It is the sort of heart-wrenching anecdote that cold-hearted political operatives love. As a hard-working family faced the nightmare of cancer, a mother’s fight to save her life was undercut by poor health insurance coverage. Her plight wasn’t important to the Republican Party and its wealthy nominee. Therefore, only Democrats can be trusted to fix America’s health-care system.

John Kerry told one version of that story in 2004. Barack Obama’s key supporters have now attacked Mitt Romney with another. Both presidential campaigns found a desperate family, took advantage of their candor, then twisted the facts for political advantage. In short, they lied.

Eight years ago, two loyal New Hampshire Democrats, Mary Ann and John Knowles of Nashua, told Sen. Kerry about their personal and financial struggles during her battle with cancer. The Massachusetts senator conveniently rewrote their painful story to fit his script, asserting in his acceptance speech at the national convention that poor health insurance coverage forced Mrs. Knowles to work every day during her chemotherapy. He knew that was not true. When a New Hampshire Sunday News correspondent uncovered his exaggerations, Kerry’s aides angrily pushed back, insisting that he had been misinterpreted. But the bogus story promptly disappeared from the nominee’s stump speech.

Last week’s lie was bigger and colder. A super PAC run by a former Barack Obama political adviser released a misleading TV ad that linked Mitt Romney’s business career to the death of the wife of a Kansas steelworker whose mill was closed by Bain Capital. Critical facts were omitted. The employee did not lose his health insurance when laid off; his wife was not diagnosed with cancer until five years later. Even liberal media such as MSNBC and PolitiFact quickly joined Republicans in condemning the ad, but the President’s campaign has refused to criticize it.

The issue at hand isn’t health care. It is basic decency. A campaign that lies about cancer will lie about absolutely anything. Any political operative who defends such ads sacrifices all credibility. A candidate who hesitates to denounce such dishonorable tactics is unworthy of any office, let alone the presidency.