Gov. Deval Patrick on Wednesday will be in Mattapan for a Democratic “unity” breakfast in the 12th Suffolk District. Massachusetts Democratic Party chair John Walsh is also expected to attend the event, which is scheduled for 9:30 a.m. at the Carter Post on Blue Hill Ave.

But the get-together could be somewhat factious, as one of the three Democrats on the Aug. 13 primary ballot will not be there, and another does not plan to endorse. Dan Cullinane, a former aide to state Rep. Marty Walsh, handily defeated Stephanie Everett, a former aide to state Sen. Sonia Chang-Diaz, and Mary Tuitt, an aide to state Rep. Gloria Fox.

Everett said she has “no problem” showing up, but she will not be endorsing Cullinane. She cited “personal reasons” but declined to publicly elaborate. “The voters voted and that’s who they want,” she said. “I wish them luck in September.”

Tuitt said she will be out of town as of Tuesday night.

Cullinane will face two independents –- Mattapan’s Lincoln Larmond and Milton’s Edmond Romulus –- in the Sept. 10 general special election. The district includes part of Dorchester, Mattapan, Hyde Park and two precincts in Milton.

Linda Dorcena Forry, a Lower Mills Democrat, set off the special election after winning the state Senate seat vacated by Jack Hart, a South Boston Democrat. The 12th Suffolk District seat in the House of Representatives was also once held by Thomas Finneran, a Mattapan Democrat and former House speaker.

Dorcena Forry, who is married to Reporter editor Bill Forry, is expected to appear at the “unity” breakfast. She stayed neutral in the Democratic primary.

State Sen. Brian A. Joyce (D-Milton), who backed Cullinane in the primary, is also on the roster of expected elected officials at the breakfast.