Within the Trump administration, Vice President Mike Pence is known as a port of calm and stability amid the churn of chaos. So on Tuesday, when he abruptly abandoned a planned trip to New Hampshire after he had already boarded Air Force Two at Joint Base Andrews in suburban Maryland, it raised immediate questions.

It is rare that something causes a vice president to abandon a publicized trip once aboard a plane. Mr. Pence’s aides said that there was no national security emergency or personal health issue that prompted the change. They said that he had boarded the plane but that it never took off. They would not say much else.

“Something came up that required the @VP to remain in Washington, DC. It’s no cause for alarm. He looks forward to rescheduling the trip to New Hampshire very soon,” wrote Mr. Pence’s press secretary, Alyssa Farah, on Twitter.

With little information to go on, theories abounded on Twitter. Mr. Pence might have been facing a national security emergency and been pulled back, people speculated. Or maybe there was a political drama taking place, with Mr. Trump summoning his second in command.