Maya Rockeymoore Cummings says she had talked with her husband about campaigning for Maryland's 7th District. The announcement comes days before she is set to have a preventive double mastectomy.
In addition to the former presidents, Kweisi Mfume, Nancy Pelosi and Hillary Clinton had been expected to speak at the service at the New Psalmist Baptist Church in Baltimore.
President Trump has repeatedly attacked Elijah Cummings' district. "I want him to come and look at my entire city," Cummings said. "I want him to see all the wonderful things that are happening."
President Trump, who has repeatedly attacked the Maryland Democrat in recent days, tweeted about the incident, saying, "Really bad news! The Baltimore house of Elijah Cummings was robbed."
His trip to Baltimore comes as the city and its long-time Rep. Elijah Cummings D-Md., have been the targets of a series of disparaging tweets by President Trump.
Speaking on Fox News, HUD Secretary Ben Carson, said he faced a "horrible dilemma" as a doctor in the city and hesitated to send some young patients back to their Baltimore homes after procedures.
The Trump Organization told staff that asking guests if they represent a foreign government would impede privacy. The House Oversight Committee's top Democrat says the policy raises "grave concerns."
Several prominent Republicans now say Jeff Sessions should recuse himself from the investigation into possible Russian interference in the 2016 election, while top Democrats ask him to resign.