Mr. Cain arrived at a Hilton hotel in suburban Virginia on Wednesday morning for what was advertised to the news media as a meeting on health care reform, which was to be followed by a news conference. But he immediately disappeared into what organizers of the meeting, Docs4PatientCare, called a “closed-door session.” Upon emerging, a mob of hotel security and other campaign personnel pushed back against the assembled photographers, and a little bit of a scrum and tussle ensued, with at least one newspaper photographer taking a hard blow to the face.

All the while, Mr. Cain, who looked unusually agitated in the center of it all, was screaming: “Excuse me! Excuse me! Excuse me!”