McDaniel's attorney, Charles Gibbs, declined to say if he would cooperate. Gibbs would also not say if Brown's recent comments, blaming McDaniel for problems with her political-action committee, might motivate him to help federal investigators.
"He and I both explored the facts that were alleged against him," Gibbs said. "And we realized that the best possible course was to plead guilty."
Brown attended City Council's weekly meeting Thursday morning, but didn't answer questions about McDaniel.
McDaniel told U.S. District Judge Mary McLaughlin that he is now unemployed after Mayor Nutter fired him two weeks ago from an $87,125-per-year job.
Nutter acted after a city Board of Ethics report detailed serious problems with Brown's political action committee, including a bogus expense filing to disguise a $3,300 personal loan repaid to Chaka "Chip" Fattah Jr., the son of U.S. Rep. Chaka Fattah.
McDaniel, who will be sentenced May 14, also told McLaughlin he is seeing a psychologist, but has not been diagnosed as mentally ill or taking any medications.
In court, Gray explained that McDaniel stole between $70,000 and $120,000 in 2010 and 2011 from Brown's political action committee and the Progressive Agenda PAC, a political action committee funded by the Laborer's District Council.
Gray said that McDaniel made bank withdrawals, wrote checks to himself and improperly transferred money between accounts.
Nutter fired McDaniel because he continued to do work for the Progressive Agenda PAC after taking a city job last year, a violation of the city's ban on political activity for employees. McDaniel lost a city job in 2005 for violating that same ban.
McDaniel, charged just last week, waived his right to have his case presented to a grand jury, to have a jury trial and to file any appeal after sentencing.
Gray said that the money McDaniel stole and the trust he abused were partially mitigated by his acceptance of responsibility and the assistance he provided in the investigation of his own actions.