WASHINGTON » When George W. Bush first ran for president, he liked to say he had inherited half of his father’s friends and all of his enemies. For Jeb Bush, now preparing his own bid for the White House, that may ring familiar.

His brother’s enemies have made themselves known in recent weeks as Jeb Bush has struggled to formulate his own take on the decisions made during the last Bush presidency. But perhaps just as important for the fledgling candidate has been the challenge in winning over his brother’s friends.

While George W. Bush himself and many in his circle, especially those closest to the family, are enthusiastic about the prospect of a third Bush presidency, many of the Republican foot soldiers who worked for the former president in his campaigns and his administration have not rushed to back his brother’s emerging operation.

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, passing up a chance to declare allegiance to the next Bush candidacy.

Some harbor the same reservations 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 Sen. 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.

"I’m neutral," said Matt Latimer, a former White House speechwriter. "If pressed, I’m inclined to adopt the Barbara Bush philosophy — enough Bushes." (Barbara Bush, the mother of the two brothers, who initially did say that, has since taken it back. "I’ve changed my mind," she said.)

Another former White House official who worked closely with George 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."

A spokesman for Jeb Bush, a former governor of Florida, said he did not take any support for granted. "Gov. Bush realizes that should he decide to move forward, he’s going to have to work to earn support across the party — just as the other prospective candidates will," said Tim Miller, the spokesman.

Many of the Bush veterans unwilling to back him cited work reasons, explaining that their current employers would not want them to take sides publicly. Some are working as academics, party officials or television pundits, and said they wanted to retain a professional detachment from any one candidate. Some said they hoped to be able to advise several of the Republican candidates, and there was no consensus for any of Bush’s opponents.

Others held back not because they oppose Bush, but because they worried that publicly supporting him would only hurt his chances by reinforcing his ties to his brother. They were acutely aware of the criticism he received when he released a list of foreign policy advisers that included many who had worked for his brother, like Paul D. Wolfowitz, the former deputy defense secretary.

Whatever the reason, the mixed emotions in the 43rd president’s team underscore a vicious quandary for Jeb Bush. Much as he wants to present himself as his own man, he cannot assume that his brother’s supporters will automatically transfer to him. So he must make the case for their support, and for that of the broader electorate, even as he labors to avoid being branded a copy of his brother.

"It is fair to say that those who are inclined to support Jeb out of loyalty to 41 or 43 have already jumped in," said Stephen Yates, who worked on national security in the George W. Bush White House and is now chairman of the Idaho Republican Party. "Everyone else is up for grabs. He’ll be able to get some of the remainder, but no advantage over others."

The distance kept by some from the 43rd president’s team reflects the reality that the two brothers have long traveled in separate political orbits, with the elder based in Texas and the younger based in Florida. There has been relatively little overlap over the years beyond family retainers.

Some of George W. Bush’s former aides were willing to publicly criticize Jeb Bush a few weeks ago when he stumbled over the question of whether he would have invaded Iraq had he known there were no unconventional weapons there.

Karl Rove, the former president’s longtime political strategist; Andrew H. Card Jr., the former White House chief of staff; and Ari Fleischer, the former press secretary, all expressed concern at the handling of the issue.

"I don’t think it would have taken his brother that long to clean it up," Card said on MSNBC. But Card was among those who offered unstinting support for Jeb Bush. "I am proudly for Jeb," he said by email.

Others offering their backing were some of the Republicans who were closest to his brother, including Margaret Spellings, the former education secretary, who runs the George W. Bush Presidential Center, and Donald L. Evans, the former president’s longtime Texas friend and commerce secretary.

"I very much support Jeb and he would be a great president if he decides to run," Evans said.

Spellings said she was "enthusiastically supporting" him. "As you might imagine, Jeb and I have a relationship independent of his brother given our shared interest in education reform, and we have worked together for many years," she said.

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?"

One who decided he did have a choice was Wayne Berman, an official in the administration of the first President George Bush, and a friend and fundraiser for George W. Bush and whose wife worked in the 43rd president’s White House. This time around, Berman is a senior adviser to Rubio.

Among those declaring neutrality rather than publicly embracing Jeb Bush’s candidacy is former Vice President Dick Cheney, who with his daughter Liz Cheney has started the Alliance for a Strong America to advocate tough national security positions among various candidates.

Others include former Secretary of State Condoleezza Rice, although she is leading Bush’s education foundation; Rove, who comments on Fox News and in The Wall Street Journal; Fleischer; Michael Gerson, a former senior White House adviser now writing for The Washington Post; Ed Gillespie, a former presidential counselor; Mark McKinnon, a campaign strategist for the former president; and Cabinet secretaries like former Attorney General John Ashcroft.

Paul J. McNulty, who served as George W. Bush’s deputy attorney general and is now president of Grove City College in Pennsylvania, said he was torn between Jeb Bush and former Gov. Mike Huckabee of Arkansas. "I’ve always been a big fan of Jeb," he said, "but I worry about his electability."

Ryan Streeter, a former domestic policy aide to George W. Bush, said the issues had changed since his former boss left office. Fiscal concerns are greater, and Republicans are more skeptical of enlarging the federal role in setting education standards for schools or expanding Medicare to cover prescription drugs, as the former president did.

As a result, said Streeter, who directs the Center for Politics and Governance at the University of Texas at Austin, "lots of 43 staffers’ views reflect those changes since many of them have stayed engaged in policy and politics."

"These issues, more than anything," he said, "will affect who they get behind in 2016."