[43]
In 1970, Biden ran for the 4th district seat on the New Castle County Council on a liberal platform that included support for public housing in the suburbs.[44][45] The seat had been held by Republican Henry R. Folsom, who was running in the 5th District following a reapportionment of council districts.[46][47][48] Biden won the general election by defeating Republican Lawrence T. Messick, and took office on January 5, 1971.[49][50] He served until January 1, 1973, and was succeeded by Democrat Francis R. Swift.[51][52] During his time on the county council, Biden opposed large highway projects, which he argued might disrupt Wilmington neighborhoods.[52]

1972 U.S. Senate campaign in Delaware
Main article: 1972 United States Senate election in Delaware
Results of the 1972 U.S. Senate election in Delaware
In 1972, Biden defeated Republican incumbent J. Caleb Boggs to become the junior U.S. senator from Delaware. He was the only Democrat willing to challenge Boggs, and with minimal campaign funds, he was given no chance of winning.[41][16] Family members managed and staffed the campaign, which relied on meeting voters face-to-face and hand-distributing position papers,[53] an approach made feasible by Delaware's small size.