“It depends whether the candidate needs help; if they’re doing very well, they need less. If they’re not, they’ll need more,” he said in an interview after a lunch stop at a barbecue restaurant during a campaign swing through Texas.

While he did not rule out dropping a billion dollars on his effort, the former mayor of New York City blanched slightly at the size of the number, before mentioning the $2.8 billion he spent on charitable contributions last year, with the bulk going to his alma mater, Johns Hopkins University.

“You know how much money a billion dollars is?” said Mr. Bloomberg. “It’s a lot of money to me. It’s a lot of money to anybody.”

No firm decisions have been made about how his operation might transition to a general election, or what form it would take, but aides say hundreds of field organizers have been offered jobs through the general election.