The nation’s largest local television chain, the Sinclair Broadcasting Group, has ordered its 62 tv stations to pre-empt its regular prime-time programming to air a controversial documentary criticizing Senator John Kerry’s record in Vietnam. The chain has network affiliates in many key swing states including Florida, Ohio, Wisconsin and Pennsylvania. Yesterday 18 Democratic Senators urged the Federal Communications Commission to investigate Sinclair’s decision to air what they view as an unpaid 90-minute attack ad against Kerry. The film, ” Stolen Honor: Wounds That Never Heal” is produced by Carlton Sherwood, a former Washington Times reporter who used to work for Department of Homeland Security director Tom Ridge while he was governor of Pennsylvania. This marks the second time this year Sinclair made headlines for its programming decisions. In April, the network refused to run an episode of Nightline when the anchor Ted Koppel read the names of every U.S. soldier killed in Iraq.