A sampling conducted largely by email of about 120 people who worked for George W. Bush — from cabinet secretaries to foreign policy advisers to advance aides — found about 25 who said they were supporting his younger brother. Fifty others said they were neutral or supporting another candidate, while the rest did not respond, apparently passing up a chance to declare allegiance to the next Bush candidacy.

Some harbor the same reservations that other Republicans do about the notion of a dynastic presidency passed from one member of a family to another. Some simply want a fresh start, concluding that the party would make a stronger case against Hillary Rodham Clinton, the likely Democratic candidate, by nominating a new figure like Senator Marco Rubio of Florida or Gov. Scott Walker of Wisconsin. Some nurse doubts about Jeb Bush specifically, even on policies he shares with his brother.

Another former White House official who worked closely with former President Bush said it would be a mistake for the country for his brother to become president. “I happen to believe the U.S. is Bushed and Clintoned out,” said this official, who like many others asked not to be named to avoid offending his former boss. “It is time for others to lead.”…

For some, though, it seemed as much obligation as fervor. “Yes,” a longtime friend and financial donor to George W. Bush said when asked if he was supporting the former president’s brother. “Do I have a choice?”