One of the largest public employee unions in the state has launched a new online ad targeting Gov. Charlie Baker’s role in the COVID-19 outbreak at the Holyoke Soldiers’ Home that resulted in the deaths of 76 veterans.The 30-second spot is the third created by the National Association of Government Employees targeting Baker over the Holyoke tragedy, and the union has put $250,000 behind the full campaign.The newest ad describes former Soldiers’ Home administrator Bennett Walsh as an “incompetent” leader who was “hand-picked” by Baker to lead the health care facility despite his lack of experience. It goes on to cite a Boston Globe Spotlight report that questioned the independence of investigator Mark Pearlstein, who was hired by Baker to probe the causes of the outbreak.Pearlstein is a former federal prosecutor and partner at McDermott Will & Emery. His investigation laid the blame at the feet of Walsh, former Veterans Affairs Secretary Francisco Urena and other lower-level administrators, but was silent on Baker and top Cabinet-level officials.”Seventy-six veterans dead due to Baker’s neglect, and his private lawyer hired to make it go away,” the narrator of the ad says. The spot ends by asking the question, “Haven’t we seen cover-ups like this before?” as an image of Baker’s face morphs into Richard Nixon.Baker’s office and his campaign could not immediately be reached for comment, but Baker has said in the past he did not interfere with Pearlstein’s report and had no prior knowledge of the decisions that were being made at Holyoke that led to the scale of the COVID-19 outbreak.The release of the latest ad comes as NAGE and other public employee unions are negotiating with Baker and his administration over the governor’s vaccine mandate, requiring all executive branch employees to be vaccinated by Oct. 17 or face disciplinary action.A spokesman for the union said additional ads will be created as part of the series, and this latest effort will appear on all major social media platforms and some cable sites.