The effort is being run by the Forward Party Victory Fund, an independent expenditure group affiliated with the Forward Party. Political director Craig Snyder said the group hopes to reach tens of thousands of voters, particularly people near the political center. He declined to disclose the campaign’s cost.

One planned message asks whether voters are tired of candidates acting as if they “own your vote,” then urges them to support Mahoney. Another video features a man identified by Snyder as a district voter saying, “I’m a Democrat, not a Socialist.” Rabb identifies as a Democratic Socialist.

The messages also invoke race, claiming Rabb won the Democratic nomination despite losing the Black vote to state Sen. Sharif Street and that white voters selected Rabb to represent much of Philadelphia’s Black community. Asked to explain the basis for the racial claim, Snyder pointed to voting margins and the racial makeup of precincts, saying the group drew its conclusion from the election map.

Rabb challenged the effort’s characterization of his primary victory. He said he won 24 of the district’s 37 wards, including eight majority-Black wards, and argued that the result reflected a broad coalition. In a statement, he said political groups should not try to divide neighbors along racial lines and that no community’s vote should be taken for granted.

Mahoney said he learned of the planned messages from a reporter. He described his campaign as focused on bringing people together and addressing problems affecting Philadelphians. Federal election rules bar independent expenditures from being coordinated with a candidate’s campaign.

The contest puts an outside group’s effort to promote an independent challenger alongside a sharply contested debate over Rabb’s political identity and the makeup of his primary support. The fund says it is backing independent candidates as an alternative to the two-party system.