New Delhi, Aug. 10 -- DETROIT - By the time Abdul El-Sayed appeared on NBC's "Meet the Press" on Sunday morning, the primary was four days behind him and the phone call he had been waiting to discuss was about to become public.

Barack Obama had called him on Friday, El-Sayed told the program. The conversation, which El-Sayed described as "very warm, very inviting," had turned to unity and to the role Michigan would play in the general election. "Sometimes, you should meet your heroes," El-Sayed said. Obama, he added, "knows the critical role that Michigan is going to play."

The call marked the clearest signal yet that the Democratic Party's most recognized figure intended to involve himself in Michigan's general election, though in what...