You are confusing Bob Kerrey (Nebraska) with John Kerry (Massachusetts.) Bob Kerrey saw a great deal of close-quarter infantry combat as a Navy Seal. John Kerry saw a couple of exchanges of fire (where by all accounts he aquitted himself well) while briefly accompanying a river patrol boat.
His primary impact on Vietnam was to strengthen the morale and fighting spirit of those NVA and VC setting mines, boobytraps and ambushes for our grunts humping the bush, when he threw replicas of his medals at the White House for the cameras in an (ultimately succeful) effort to score chicks for himself.
Stand corrected.