Sen. Ed Markey’s campaign released an ad this week meant to tout his progressive support. Instead, the ad — which featured quick cuts of his top endorsers, Sens. Bernie Sanders (I-Vermont) and Elizabeth Warren (D-Massachusetts), along with Rep. Ayanna Pressley (D-Massachusetts) — only highlighted the progressive left’s gerontocracy problem that has dogged the Markey campaign for months. Markey is 80 and, after 53 years in elected office, is running for reelection to another six-year term, while Sanders, 84, and Warren, 77, are currently serving terms through 2030. The Democratic gerontocracy issue is well documented. There was Joe Biden’s forced departure...