Republican presidential candidate Donald Trump speaks during a rally at Ladd-Peebles Stadium on August 21, 2015 in Mobile, Alabama. The Trump campaign moved tonight's rally to a larger stadium to accommodate demand. (Photo by Mark Wallheiser/Getty Images)

MOBILE, Ala. -- Donald Trump's rallies have the rhythm all their own, all captured live on cable TV. There is the press conference, typically first, at which the Republican presidential front-runner spars for 10 to 15 minutes with reporters, sparing no disdain. There is the mega-rally, and the hour-long speech that lasts long beyond the utterance of the phrase "and finally." Then, to the righteous screeching of Twisted Sister, come the handshakes and the exit. Every time, Trump makes news by pouring disdain on a rival -- Jeb Bush, Hillary Clinton, whoever's earned it that day.

The largest rally of Trump's campaign so far broke with this pattern. A press conference was scheduled between Trump's arrival (by plane, then motorcade) and speech. But the mogul felt the air at the Ladd Peebles stadium -- a thick, soupy heat that thousands had baked in all day -- and word spread that the press conference was bumped until after the speech. As Trump wrapped, reporters raced out of the stadium and over to the VIP lounge that had been turned into a Trump soapbox, complete with blue curtain, state and national flags, and a podium. The TV reporters who'd been grilling Trump on immigration staked out front-row seats; local reporters getting their first crack at Trump thumbed through their question.

And then: Nothing. Reporters and Trump guests, including Alabama's secretary of state, found themselves in a Trump-less room. As Trump stepped off the stage, signing copies of his 1987 best-seller “The Art of the Deal” and shaking hands, he ducked quickly toward a waiting caravan of seven Cadillac Escalades. Six of them were black; Trump’s was white. The scheduled news conference never came up. One security guard said, “On to the airport!” as Trump settled into the white-leather front seat. He was followed by his campaign manager, Corey Lewandowski, and his son, Eric. Off they went, past waiting reporters and a local television camera, followed by Sen. Jeff Sessions in his own Cadillac.

That meant no one asked Trump, in time for that night's packages, about what seemed to be a half-full stadium that the campaign had hoped to turn into a fire hazard. Only a few reporters who followed Trump to the airport got to watch him leave and ask questions. Long after Trump left the stadium, Colby Cooper, the chief of staff of Mobile’s mayor, emerged to insist that the city counted 30,000 people at the rally, still short of the 35,000 tickets that had been distributed.

Robert Costa contributed reporting.