The breakneck assembly process culminated several hours later in a rally that the campaign said had attracted more than 1,300 — its biggest crowd in the state to date.

“Advance people want predictability, and they want to know that somebody is going to do a great job,” said Doug Landry, the national advance lead for Hillary Clinton’s 2016 primary campaign, who has largely stayed out of this cycle. (Advance people are campaign staffers who are generally responsible for planning and executing events.)

This is Mr. Malloy’s second primary cycle producing a plethora of presidential events, after working for both Mr. Sanders’s and Hillary Clinton’s campaigns leading up to the 2016 primary. The company is nonpartisan, but Mr. Malloy is a former Democratic state representative and has connections in the party.

His experience creates a network effect in which the more events he does, the more he is trusted to have mastered the state and its venues. “If you consistently perform well, they will call you over and over again,” Mr. Landry said.

Mr. Malloy knows which halls already have adequate lighting and which he will need to supplement, and which fire marshals are sticklers for neat rows of chairs.

He packs chalk to get out stains; ibuprofen for headaches and portable cellphone chargers to prevent them; and a portable printer that has proved handy to candidates at the last minute. Malloy Events owns $25,000 worth of flags, Mr. Malloy estimated; a V.F.W. brochure on proper flag protocol sits on his pickup truck’s dashboard. (“The blue unit has to be in the top left,” he said.)