By Bill Berkrot NEW YORK (Reuters) – Hillary Clinton’s campaign promise on Tuesday to cap prescription drug costs for U.S. consumers lends weight to efforts by health insurers, doctors’ groups and consumers to address skyrocketing prices, industry experts said. Clinton, in the lead among Democratic presidential candidates, unveiled a plan that includes a $250 monthly cap on out-of-pocket costs prescription drugs, allowing the Medicare plan for the elderly to negotiate drug pricing and permitting Americans to purchase drugs from other countries at lower cost. Clinton is seeking the Democratic nomination for the November 2016 presidential election.