“I will be making a decision over the next three- to four-day period of time, and I think it will be a decision that will be a very good decision for a lot of people,” he added.

Mr. Trump said that he was not basing his vice-presidential selection on fund-raising prowess or potential, and indicated that he had had enough experience with many of those he has been considering for the job that their tryouts on the campaign trail would not necessarily be determinative.

“I’ve been with these people for a long time — I know them,” Mr. Trump said, specifically invoking Gov. Chris Christie of New Jersey and Newt Gingrich, the former House speaker. “Christie was excellent yesterday and Newt is excellent.” Mr. Trump will appear on Tuesday night in Indiana with Gov. Mike Pence, who has risen in the estimation of many of the nominee’s advisers.

Mr. Trump said his decision was largely coming down to instinct. “A lot of is gut. A lot of it is,” he said. “My whole life has been about gut.”

He also suggested that he would consider polling in states like heavily Democratic Connecticut, which he again said he believed he could put in play in November.

Asked for quick thoughts about each of the candidates he is known to be considering, Mr. Trump played along.