A newly formed political committee has spent $480,000 on a major television advertising buy on behalf of mayoral hopeful Martin J. Walsh, according to disclosures filed Thursday with the state Office of Campaign and Political Finance.

The political action committee, which calls itself One Boston, will not be required to disclose its financial backers until January, long after Tuesday’s mayoral election.

Two expenditure reports were filed with the state noting advertising buys of $480,000. Jocelyn Hutt, the only name listed on paperwork for One Boston, said in an e-mail that the media buy was $480,000, which suggests that one of the reports was a duplicate.

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Walsh’s mayoral campaign has been buoyed by a flood of outside money totaling $2.3 million. As of Oct. 15, Walsh’s official campaign had only spent $1.7 million.

Outside groups have spent almost five times more for Walsh than for his opponent, City Councilor John R. Connolly, who has been supported by $563,000 in spending by education groups.

The other outside groups backing Walsh have been funded by organized labor. They include Working America, which is the political arm of the national AFL-CIO, and American Working Families, a political action committee based in Virginia and funded by unions.

One Boston filed paperwork with the state on Oct. 24 to form a political action committee. The group listed Hutt, of Congreve Street in Roslindale, as both the chairman and treasurer. No other names were listed.

Hutt said in the e-mail that “donors will be disclosed on the next regularly scheduled PAC report,” which is in January, after the mayoral election. Hutt did not immediately respond to a request for a phone interview.

In recent years, Hutt has not personally contributed to political candidates in Massachusetts, according to the state Office of Campaign and Political Finance. Hutt is a senior account manager for the east coast division of DRS and Associates, which describes itself as boutique public relations, advertising, and marketing agency specializing in luxury brands.