As an organization, the Committee of Seventy changed little in the 1920s. It attempted to strengthen its ties to other civic organizations in Philadelphia and chose to diversify its membership by including women.
Early in the 1920s, the Committee of Seventy began to expand its scope of interest to include City finances as part of its concern for good government. At first, Seventy reviewed public works contracts that the City granted to private businesses. For many years, Philadelphia taxpayers had paid exorbitant sums for the construction and management of second-rate public works, such as the trolley and subway systems. Much of the money went to line the pockets of Republican bosses and select businessmen. Acting as a fiscal watchdog, Seventy went public with its criticism of fraudulent contracts and excessive spending.
Although Seventy had some success reforming Philadelphia 's elections in the first part of the century, many problems remained. Seventy continued to monitor elections in the 1920s and 1930s, and it acted on complaints received during each election. Cases were prepared and presented to the District Attorney if sufficient evidence was available to pursue a conviction. Seventy’s investigation of the 1926 U.S. Senatorial contest ended with the ouster of the newly elected Republican boss William Vare on charges of voter fraud. The Senate refused to seat Vare because his family had a notorious reputation for fraudulent voter registration, purchase of votes from poor citizens, and ballot-box stuffing, among other illegal practices. After three years of investigation and delay Vare was still denied his seat in the U.S. Senate, due to the fact that he had spent too lavishly on the Republican primary. The public awareness of Vare Machine misconduct can be accounted for by the efforts of the Committee.
Between 1925 and 1927, Seventy secured the convictions of approximately forty registrars and election officers on Election Code violations. Seventy also continued to push for long-term election reform through legislation. Because of the efforts of Seventy, the procedures for voter registration were tightened to discourage vote fraud through the misuse of registration binders.
As an extension of its concern for honest elections, Seventy launched a campaign in 1928 to have mechanical voting machines installed in every Philadelphia voting division. Seventy argued that the machines would standardize voting procedures across the city, and would eliminate some methods of falsifying election returns. Against the stiff opposition of the Republican-controlled County Commission, the agency in charge of elections, Seventy eventually prevailed. Although voting machines would not be installed city-wide until 1946, they were used in most wards in the 1930s.
In the 1930s, Seventy sued to stop the political manipulations of Mayor S. David Wilson with the City's Sinking Fund and gas works and even drew up plans by which the City could relieve its indebtedness. In the 1930s, Seventy also made an effort to recruit young citizens, recognizing that many of its members were elderly veterans of the reform movement. These new members worked as volunteers to collect and analyze data on numerous topics, and gave Seventy the ability to conduct its investigations at little expense. Seventy received some of its funding from foundation grants, but members continued to supply the majority of the funds for its operating budget. Moreover, near the end of the decade, Seventy also organized a War Time Round Table to discuss the issues surrounding WWII on the radio.