Jeb Bush has lost his frontrunner status and now rivals say he's getting nasty

On Monday, news broke that Danny Diaz will be the campaign manager when former Florida Gov. Jeb Bush (R) launches his expected White House bid on June 15.

As the Wall Street Journal reported, the position was originally "expected" to go to David Kochel, another operative who will instead serve as Bush's chief strategist.

Business Insider had several conversations with aides to other Republican 2016 presidential campaigns who said they believe this staff switchup is evidence the Bush campaign is changing its strategy amid disappointing poll numbers and failed efforts to eliminate opponents.

"The strategy they were previewing with everybody is already changing substantially and they haven't even announced their campaign yet," a rival 2016 GOP operative said of Bush's team.

Overall, the operatives who talked with Business Insider said they believe Bush is abandoning efforts to run a positive, above the fray campaign. Last year, when he began publicly discussing a potential candidacy, Bush vowed to have a "hopeful, optimistic message" and said he would campaign with "joy in my heart." However, this month, Bush has launched a series of attacks on his Republican rivals that some observers have pegged as a sign of a strategic shift.

The operative suggested naming Diaz as his campaign manager was further indication Bush is pursuing a more aggressive strategy.

"Putting one of the best opposition research guys in the business in charge is a dramatic change from Jeb's previous 'joyful' message. This is essentially going back to square one and scrapping the original strategy they touted at the beginning of the year," they explained.

An aide for another rival Republican presidential campaign echoed the notion Bush is changing course and attributed it to disappointing poll numbers.

"They're having to change their strategy and attack much earlier," they said.

The aide also pointed to a Washington Post story from last month where Robert Costa and Matea Gold reported there were "pockets of anxiety ... percolating among Bush supporters" who are worried he isn't more aggressively attacking opponents at this early stage of the race.

"Those pockets have clearly called for action," the operative said.

In a conversation with Business Insider, Tim Miller, Bush's communications director, disputed the idea the campaign has changed course.

"I think he's certainly capable of being happy and aggressive," Miller said of Bush.

Miller also addressed the decision to tap Danny Diaz as campaign manager rather than David Kochel. He said it "makes sense" for the pair to have their current roles.

"With regards to Dave and Danny, Governor Bush brought together a bunch of talented operatives that are focused on advancing his message as he looks to make his big announcement next week. He wanted to make sure that everyone was serving the best and highest purpose," Miller said. "Danny is suited towards making rapid day-to-day decisions and making sure that the ship is moving forward every day. ... David is going to be able to focus in his role as chief strategist for providing strategic framework for how Governor Bush will win primaries, and caucuses, and eventually the nomination and presidency. Two people are required to fulfill those roles in a successful campaign."

While Bush's team denies they're making any strategic shifts with staffing and tone, rivals point to another indication Bush hoped to run a different type of campaign. Earlier this year, there were multiple reports that Bush's team hoped an early fundraising blitz would help him secure frontrunner status and even scare off some potential opponents.

"Look at how he was sort of previewing his potential candidacy especially back in December ... talking about running with joy in his heart ... the massive fundraising that was supposed to push people out," the rival operative said. "None of that seems to be falling into place."

Dr. Larry Sabato, a political scientist and analyst who is the director of the University of Virginia Center for Politics and runs the Crystal Ball, a site that maintains a detailed analysis of the 2016 field, believes it's obvious Bush's effort to push out his opponents didn't pan out. In an email to Business Insider, Sabato attributed this to the fact there are enough interested megadonors to support multiple candidates.

"The reason is clear: There's a billionaire in (almost) every pot," Sabato wrote.

Though he described Bush as a top contender, Sabato also said he definitely hasn't secured frontrunner status.

"At the Crystal Ball we regularly update our ratings. Jeb Bush continues to be a first-tier candidate along with Marco Rubio and Scott Walker. We don't believe there is a single front runner in this enormous field. We would term anyone in our first tier a front runner," Sabato wrote. "Bush hasn't intimidated anyone and isn't close to the commanding position his father and brother were at this point in the cycle. But Bush is still the preferred choice of many if not most big donors and elected leaders. Bush is in a kind of limbo on frontrunner status just now."

For his part, Miller, Bush's communications director, disputed the idea the campaign ever planned on Bush being out in front.

"Governor Bush is well aware that he's going to have to earn every vote and work for it and that this is an extremely competitive primary field and is under no illusion that this is going to be anything but a hard fought race," Miller said. "Anybody who says that he or our team felt like this was going to be some sort of walk in the park is misrepresenting our views. We always knew that this was going to be a competitive field and this was going to be a hard fought effort."