Bush is making staff moves ahead of his expected campaign launch next week. (Alex Wong/Getty Images)

This story has been updated.

Jeb Bush is just days away from formally launching his presidential campaign and already a shake-up is underway.

In a surprise move Monday, Bush tapped Republican strategist Danny Diaz to serve as his campaign manager, shoving aside another aide, David Kochel, to head his still-unofficial presidential operation.

Diaz’s promotion is a frank acknowledgment that Bush’s six-month “exploratory phase” has not met expectations and that the former Florida governor needed a new consultant to take the reins ahead of his campaign kickoff in Miami on Monday.

Bush has raised more than $100 million since announcing his presidential interest in December, but he has sunk in opinion polls as the GOP field has grown with credible challengers. Bush has been dogged by deep skepticism within the GOP base about his trustworthiness and viability, and he has struggled to differentiate himself from his brother and father, both former presidents.

The shake-up also threatens to overshadow Bush’s five-day swing through Europe beginning Tuesday, when he arrives in Berlin to speak at an economic summit before heading to Poland and Estonia. The tour is part of an effort to polish Bush’s foreign policy bona fides ahead of his announcement.

“Jeb’s had a pretty bumpy campaign road so far, and he needed to make some changes,” said Douglas E. Gross, a Bush family friend in Iowa who is not aligned with any candidate. “One of the keys to success is getting the right people into the right seats on the bus.”

The restructuring of Bush’s staff was unexpected given that Bush aides, donors and friends had said for months that Kochel — whom Bush successfully wooed away from Mitt Romney’s inner circle earlier this year — was poised to serve as campaign manager.

The arrangement comes after a rough period and tense discussions among Bush loyalists, and conversations between two of his closest advisers, Sally Bradshaw and Mike Murphy, about the campaign’s setup, according to people familiar with Bush.

Bradshaw wrote in an e-mail that “Mike Murphy and I have been friends for over 18 years. It is laughable to think there is any tension between the two of us.” Murphy’s e-mail read that there’s “zero tension between Sally and me. . . . No idea where that silliness came from.”

Starting Monday, Bradshaw and Murphy will go separate ways. She will become a senior campaign adviser and he will take control of Bush’s super PAC, Right to Rise, and is legally barred from coordinating with the campaign, his aides said.

Diaz, a 39-year-old D.C. native, has developed a close relationship with Bush since joining his orbit in February as a media consultant, endearing himself to the candidate with his hard-driving manner, according to informed Republicans. Diaz was described as a “lion” and “tiger” by others Monday. Bush “very much likes Danny’s vigor and intensity,” a campaign official said.

Veteran Bush associates said they knew little about Diaz — Gross said he didn’t know him “from a bale of hay.” Younger professionals more closely involved in recent campaigns gave him generally positive reviews.

Steve Schmidt, a former adviser on the 2008 presidential campaign of Sen. John McCain (R-Ariz.), called Diaz “the Jim Harbaugh of politics,” referring to the University of Michigan’s intensely competitive football coach. “The degree to which there is a feeling of not having it together, that era is coming to a decisive end.” But another GOP hand who worked with Diaz on campaigns and is close to the Bush camp described Diaz as “a hair-on-fire guy” prone to lose his temper.

Strategist Stuart Stevens — who is close with Kochel and worked as Romney’s chief strategist in 2012 — said: “Dave is a first-rate talent and as good as they come. Every campaign has to chart its own path. But any campaign is lucky to have Kochel working for them.”

The staff reshuffling was first reported Monday by the Wall Street Journal.

Diaz will take a leave from Washington-based FP1 Strategies, which had been hired by Bush to handle media strategy. In that role, he was spotted frequently on the campaign trail alongside Bush. Diaz’s business partner, Jon Downs, will serve as head of Bush’s media and advertising.

The firm’s clients have included FWD.us, a lobbying group established by Facebook founder Mark Zuckerberg and other Silicon Valley-area technology executives to push Congress to pass comprehensive immigration reform — an idea that Bush has endorsed in the past. Diaz is also a former spokesman at the Republican National Committee and more recently worked on the successful gubernatorialcampaigns of Republicans Doug Ducey of Arizona and Susana Martinez of New Mexico.

Kochel, meanwhile, will serve as a chief strategist “and build and oversee a political operation to achieve success in the early states and beyond,” said Tim Miller, who will serve as Bush’s communications director. Kochel is expected to concentrate primarily on building up Bush in Iowa, New Hampshire, Nevada and South Carolina, where he’s lagging in polls.

It was Kochel’s decision in January to join Bush’s kitchen cabinet that first signaled how seriously Bush was preparing for a White House bid and delivered a blow to the potential reemergence of Romney, the 2012 nominee who was considering another run.

Other Republicans close to Bush who demanded anonymity to speak about private conversations said the moves were a sign of the campaign’s adaptability to a race that has been tumultuous and Bush’s need to improve in the early states, where they would like to see him win at least one state in the opening primaries.

Following next Monday’s announcement, Bush is scheduled to make stops in New Hampshire, Iowa, South Carolina and Washington, where he will attend a fundraiser and speak at a conference hosted by the Faith and Freedom Coalition.

In more widely anticipated moves shared Monday by campaign aides, Bush’s high-level staffers will also include Scott Jennings, who will serve as a political adviser. He’s a former political aide to Senate Majority Leader Mitch McConnell (R-Ky.).

In addition to Miller’s role as communications director, Kristy Campbell will serve as campaign press secretary. She worked for Bush’s nonprofit education foundation and served as his gubernatorial press secretary for a time. Michael Steel, a former spokesman for House Speaker John A. Boehner (R-Ohio), also has moved to Miami to take a senior communications role.

Heather Larrison, who has spent the past several months raising millions of dollars for Bush’s super PAC, will serve as the campaign finance director. Brenda Gianiny, who served as pollster for George W. Bush’s White House and on his 2004 reelection campaign, will lead the research and polling team. Alex Lundry, a corporate and political consultant who worked on Romney’s 2012 campaign, will handle data analytics.

Dan Balz and Philip Rucker contributed to this report.