An independent US Senate candidate is convinced he is a victim of sinister political forces in Cambridge City Hall who are demanding he remove an anti-Elizabeth Warren sign that hangs from his campaign bus on Concord Avenue.
Shiva Ayyadurai, who began running in the Republican primary but shifted to an independent candidacy late last year, claims in a federal lawsuit, which he says he filed this week, that city officials are violating his First Amendment rights and carrying out political retaliation against him because he is attacking Warren over her claims to Native American heritage.
In a press release, he charged that Cambridge's actions were a "vendetta by city officials who are supporters of Elizabeth Warren."
When asked to elaborate, Ayyadurai declined.
"The evidence we have will be presented in court,'' he said in an e-mail response to the Globe inquiry.
The suit claims that the city, citing anonymous complaints, had notified the campaign on April 4 that its sign, which is on bus parked on the edge of his company's lot, is violating the city building codes.
The city, according to the lawsuit, threatened to impose a $300-a-day fine until it is removed.
Ayyadurai's suits claims because the sign is on the bus, which he says travels from time to time on the campaign trail, and not on the building, the sign does violate any ordinance.
He is asking the federal court to enjoin the city from imposing the fine and from "making further threats . . . for the political message'' displayed on the bus.
Ayyadurai's beef is that the city never complained until the sign — which had originally only touted his candidacy — was changed last June to display a photo of him and Warren, whose image is given a Native American headband. The words states: "Only a REAL INDIAN Can Defeat the Fake Indian."
Cambridge officials were not commenting.
"It is the city's practice to not comment on ongoing litigation,'' said Lee Gianetti, the city's communications director.