Homeland Security Secretary Jeh Johnson told a Senate hearing Tuesday that 18 states have taken up his agency’s offer to help improve cyber security for their election systems, in the wake of suspected breaches blamed on Russian hackers. “We are seeing a limited number of instances where there have been efforts through cyber intrusions to get into the online presence of various state election agencies. And, one or two of them have been successful, others have not,” Johnson said at a Senate Homeland Security Committee hearing. The issue of the integrity of US elections has been a prominent one on the presidential campaign trail, with Republican presidential nominee Donald Trump and Democratic Sen. Harry Reid each raising concerns about possible rigging of the results. Both Trump and his Democratic rival, Hillary Clinton, said at Monday’s debate that they would respect the election results. Asked by Sen. Jon Tester, D-Montana, whether hackers are seeking to change votes, Johnson said: “What we are seeing are efforts to get into voter registration rolls, the identity of registered voters, things of that nature, not to change a ballot count.”