From The Federalist:
According to Soviet documents unearthed in the early 1990’s, [Ted] Kennedy literally asked the Soviets, avowed enemies of the U.S., to intervene on behalf of the Democratic party in the 1984 elections. Kennedy’s communist communique was so secret that it was not discovered until 1991…
You can read the full KGB memo detailing Kennedy’s secret letter and request for electoral intervention here.