In the heart of Harlem early this year, U.S. Rep. Charles Rangel sat down at Sylvia's Restaurant for a coffee with a potential rival and asked him not to run for the seat the congressman has held for more than four decades.

"I didn't persuade him," Mr. Rangel said of his January sit-down with the Rev. Michael Walrond Jr., a Harlem pastor. "I had hoped maybe."

There...