Trump-tied Ballard Partners cut ties with its Government of the District of Columbia client due to the escalating feud between Washington Mayor Muriel Bowser and the president.
That tension rose following the deployment of active-duty US troops to the DC area in the wake of the Black Lives Matter protest.
Bowser, who has marched with the demonstrators, on June 7 called the deployment an "invasion" and demanded the withdrawal of the troops.
She also had "Black Lives Matter" painted on two blocks leading to the White House.
Trump attacked the mayor on Twitter May 30, saying she is "always looking for money and help" and falsely charged that Bowser withheld DC police from demonstration.
The president on June 7 said he ordered the National Guard to withdraw from DC now that "everything is under perfect control." This followed criticism from retired generals about Trump's militarizing the response to the protests.
There are about 5,000 National Guard soldiers in Washington. About 1,200 of them are members of the DC National Guard.
Brian Ballard, who chaired the Trump Victory fundraising organization in Florida during the 2016 presidential campaign, headed the three-person lobbying team for Washington.