Later a resident of
Mount Holly, Costa was one of the first residents of Levittown, before it was renamed as
Willingboro Township, New Jersey. She served on the Willingboro Township Library Board of Trustees in 1959 and from 1962 to 1966. She chaired the township's Zoning Board from 1969 to 1973. In 1964, she was elected chair of the Willingboro Democratic organization. Costa became involved in politics after working on
John F. Kennedy's
presidential campaign in 1960. She was present in October when Kennedy campaigned in Willingboro.
Burlington County Freeholder In 1970, Costa ran for
Burlington County freeholder. She was opposed by the Burlington County Democratic Party organization, which supported county clerk Charles Ehrlich and Vincent Rogliano, who had withdrawn from a campaign for Congress in order to clear the field for
Charles B. Yates. Although she ran
off the line, she ran with incumbent U.S. senator
Harrison A. Williams, since the Burlington organization had given the line to his challenger,
Frank J. Guarini. She lost the primary by a large margin, running third in every municipality except
New Hanover, which she narrowly won. However, Costa quickly had another opportunity to run when Richard Nixon appointed freeholder Anthony Greski as
U.S. Marshal for the District of New Jersey. In the special election to complete Greski's term, Costa lost to Republican Frank Lockhart by eighteen votes out of more than 70,000 cast after a recount. In 1971, Costa defeated Lockhart in a recount by about four thousand votes. In 1974, she was re-elected over former freeholder James A. Miller in a landslide following the
Watergate scandal. In 1976, Costa was the Democratic nominee for New Jersey's 6th congressional district, which included parts of Camden, Burlington and Ocean counties. Although
Jimmy Carter nearly carried the district against incumbent
Gerald Ford, Costa was defeated by incumbent
Edwin B. Forsythe in a landslide. She received only forty percent of the vote. In 1977, Charles B. Yates left his Assembly seat in order to run successfully for
New Jersey Senate. Costa considered campaigning for his seat, but Willingboro mayor
Barbara Kalik quickly consolidated support. Costa opted to run for re-election and won another landslide over
Mount Laurel councilman Michael Traino. She was re-elected to a fourth term over
Florence councilman Emmett Spurlock in 1980, carrying 35 out of 40 municipalities in the county. == New Jersey Legislature ==