Former Florida governor Jeb Bush on Dec. 2 in Coral Gables, Fla. Bush strategist Mike Murphy has been telling potential campaign staffers not to sign up to work for another presidential candidate and to expect Bush’s announcement soon. (J Pat Carter/AP)

Jeb Bush and his emissaries are sending increasingly strong signals that the former Florida governor is gearing up for a 2016 presidential campaign, with associates saying he could announce his intentions within a month.

Bush recently e-mailed major Republican donors asking them to, as several of them put it, “keep your powder dry.” His allies are urging would-be bundlers not to commit to New Jersey Gov. Chris Christie or other potential rivals. Bush’s top strategist, Mike Murphy, has also been telling potential campaign staffers not to sign up to work for another candidate and to expect Bush’s announcement soon.

Out of public office for eight years, Bush has a thicket of business interests — including massive overseas investment funds — that he is working to untangle himself from before a campaign begins. As one confidant said, “He says he knows he has to wrap it up.”

If Bush launches a presidential exploratory committee or otherwise declares his intentions in coming weeks, he would immediately increase the pressure on potential rivals in both parties to make their own decisions quickly. Hillary Rodham Clinton, the presumed Democratic front-runner, has signaled that she could wait until spring to launch a campaign, while many Republicans have been waiting for Bush to make a move.

For Bush, allies said, waiting until spring to decide on a campaign would carry serious risks. The competition is already underway among a dozen or so ambitious Republican hopefuls to woo donors and sign talented staff.

Some senior Republicans in communication with Bush said they have concluded he is almost certain to run. His family — once averse to a campaign — is now on board with a run. Bush also has slimmed down: He is working with a new personal trainer after a knee surgery, according to the Miami Herald, and lost 15 pounds in recent weeks.

Asked whether he saw any reason Bush would not run, one confidant who has been in touch with the former governor said, “I don’t know of anything.” This person, who like some others interviewed spoke on the condition of anonymity to talk candidly about the conversations, said Bush sees value in taking his time before deciding.

“It’s easier to be a prospective candidate than a candidate,” this person said.

A second Bush confidant said: “He’s not playing games. He’s being very sincere and honest with folks and going through the things that really matter to him. Within a month, we’ll know.”

Bush has said previously that he would decide by the end of this year or early in 2015. Aides said that timeline has not changed.

“Governor Bush has not made a decision about whether or not he will run in 2016,” spokeswoman Kristy Campbell said. “We are not going to weigh in on the decision-making process beyond what he has said to date.”

In recent weeks, Bush has been talking with Republican leaders and strategists about how to effectively address his support for immigration reform and the education standards known as Common Core. Both positions are anathema to conservative activists, especially in Iowa, home to the nation’s first presidential caucuses.

During a recent speech at a Wall Street Journal event, Bush said anyone running for president should be prepared “to lose the primary to win the general [election] without violating your principles.”

Fred Malek, a longtime Republican fundraiser, said Bush’s remarks indicated that “he’s giving it some serious and deliberate thought.”

In preparation for a campaign, Bush is beginning to disentangle himself from some business relationships, according to two people close to him. Bush, who has worked for Lehman Brothers, Barclays and private-equity firms, also is conducting opposition research on himself to study his vulnerabilities, as Politico first reported.

“He’s not going to run for president without having an understanding of what a Hillary Clinton campaign would do ­research-wise,” one of those people said.

Bloomberg Businessweek, in a story Thursday headlined “Jeb Bush has a Mitt Romney problem,” reported on documents filed last month with the Securities and Exchange Commission listing Bush as chairman and manager of BH Global Aviation, an offshore private-equity fund that raised $61 million in September, largely from foreign investors.

Bush’s advisers said the story does not provide a full portrait of Bush’s business activities. Some GOP donors and operatives were alarmed by the report. But Bush’s advisers told allies who have asked about it that Bush is proud of his investment work and defends the free-enterprise system.

“Nothing related to Governor Bush’s business activities would hinder a run in any way, should that be what he decides to do,” Campbell said.

Bush is entrusting much of his political preparations to Murphy, who lives in California, and Sally Bradshaw, a longtime counselor in Florida. They helped Bush sharpen his pitch on the campaign trail this fall and are consulting with potential campaign staffers nationally and in key states.

Bush’s team is also trying to quiet whispers in Beltway circles that his political skills are rusty. Murphy insisted that Bush is as engaged as ever, from keeping tabs on national affairs on his iPad to regularly calling Republican lawmakers and officials.

“Anybody who knows Jeb Bush and has watched him campaign or devour public policy knows the word ‘rust’ is not in his dictionary,” Murphy said.

Even with his stealth campaign underway, Bush is avoiding overt moves that might spark unwelcome speculation.

On Monday, Bush is traveling to Columbia, S.C., to deliver the winter commencement address at the University of South Carolina. Shortly after the ceremony, the state Republican Party’s executive committee is scheduled to meet a few blocks away. Any presidential candidate would want to court these party leaders in the state that hosts the first primary in the South. But Bush is not planning to visit with them, flying in and out of the state without doing any politicking.

Judd Gregg, a former Republican senator from New Hampshire, said he is not surprised that Bush is not doing early organizing. “He’s so well-known and he already has the credibility he needs to attract an organization to him,” Gregg said.

In recent days, Romney allies have been reaching out to his former donors and staff to gauge whether they would be available to work for Romney again even if Bush runs, according to a former senior Romney campaign official.

Across the Republican firmament, the topic du jour has been, What will Jeb do? Party insiders ready to embrace Bush are dissecting his every move and statement — as well as those of his family members — for clues about his thinking.

At a Christmas party for donors at George W. Bush’s presidential library in Dallas on Saturday, guests are expected to be abuzz about the possibility of yet another Bush in the White House. Ray Washburne, a Dallas investor who serves as finance chair of the Republican National Committee, said Jeb Bush is “the big elephant in the room.”

Mel Sembler, a former ambassador and longtime Bush family friend, said, “I think we’re going to see Jeb run.”

Robert Costa and Karen Tumulty contributed to this report.