The tale Republicans tell is the reason they often carry an edge on the economy. As someone who has spent the bulk of his career working in and around progressive politics, I find Democrats' failure to grasp this core concept increasingly befuddling because it's so self-defeating. Granted, I have a dog (or two) in the fight. But there's no denying that Messrs. Clinton and Obama inherited flagging economies from their predecessors and handed their successors engines of prosperity. I don't understand how anyone in the progressive community still believes there's political upside to dismissing progressive presidential accomplishments. During the 2016 primaries, the left-wing Nation magazine ran an article titled "Note to Hillary: Clintonomics Was a Disaster for Most Americans." On the campaign trail last year, Mr. Biden called fellow Democrats' criticism of Mr. Obama in the Detroit debate "bizarre." Take the precedent that's most frequently at issue today—the Recovery Act of 2009. Mr. Obama's economic strategy not only prevented the Great Recession from morphing into a full-fledged depression, but sparked a record-setting recovery. The legislation he signed was far bigger than any previous stimulus bill and was as robust as Congress would allow. It was also only one part of Mr. Obama's broader economic agenda, which included restructuring General Motors and Chrysler, investing in the early renewable energy industry, expanding healthcare coverage and stabilizing the financial system. Most important, the Obama administration's comprehensive effort was a resounding success. During Mr. Obama's tenure, the economy flipped from losing an average of 362,000 a month during his first year in office to gaining an average of 200,000 a month during his last year. Why would any progressive want to label any of that as "minimalist"? Take the Clinton administration. On the issues progressives talk most about today—job creation, poverty reduction, the list goes on—Mr. Clinton's eight years often set economic records. During his tenure, the income gap separating the poorest and richest fifths of American families dramatically narrowed. The economy gained more than 20 million jobs. In 1995 Clinton was so intent on saving Medicare and Medicaid from cuts that he stood firm during a Republican-led government shutdown. Far from claiming that he was some sort of "Republican lite," progressives should own Mr. Clinton's accomplishments because they provide a foundation for what we want to do in the future. Decades ago, Reagan coined what many call the 11th commandment: "Thou shalt not speak ill of another Republican." Democrats don't need to pretend that every Democrat who ever held office was infallible.