Jeb Bush’s campaign is taking a more aggressive and negative tone against Marco Rubio, his chief rival for the establishment mantle in the race for Republican presidential nomination.

For months the Bush and Rubio campaigns have sparred behind the scenes or with veiled or soft criticisms of one another. 

But with Wednesday’s debate highlighting Bush’s struggle and Rubio’s rise, the Bush campaign has begun to move beyond attacks on Rubio’s Senate voting record and relative inexperience into far more personal territory as it seeks to keep the up-and-comer at bay.

“They don’t want to let Rubio get too far out ahead or build too much momentum,” said Republican strategist Ford O’Connell. “He had a ground-breaking moment at that last debate and I think they’d like to cut his knees out before the next one.”

Bush’s attack against Rubio for abandoning his Senate work for the campaign trail backfired at Wednesday’s debate, as the junior senator came prepared to shut down Bush on the issue.

But it turns out, the Senate voting complaint was one of the Bush campaign's milder attacks on Rubio.  

Late Thursday, U.S. News & World Report obtained a PowerPoint file presented to Bush donors at a Houston confab earlier this week. One slide dug up past controversies around Rubio and took some exceedingly personal digs.

“Misuse of state part credit cards, taxpayer funds and ties to scandal-tarred former Congressman David Rivera takes away line of attack on Hillary Clinton,” says one bullet point. “Closeness with Norman Braman, who doubles as personal benefactor raises major ethical questions,” says another. Braman is a billionaire Florida auto-dealer and is one of Rubio's most generous donors.

The Bush campaign also hit Rubio for “having no credible experience beyond government,” for never managing “anything larger than two dozen people,” and mocked his “tomorrow versus yesterday” argument, saying it would be dismantled by the media because he’s likely to be running against the first woman presidential candidate.

A final bullet point reads, ominously: “Those who have looked into Marco’s background in the past have been concerned with what they have found.”

Top Bush donors and fundraisers, still stinging from Rubio’s debate triumph, are divided on whether Bush, who has failed to find his footing in the first three debates, should be going negative against his former protégé.

In interviews with The Hill over the past two days, a number of Bush’s major donors, fundraisers, and operatives have expressed mixed feelings about the wisdom of challenging Rubio — a gifted public speaker — at a game they believe Bush cannot possibly win. 

One of Bush’s most generous super-PAC donors and a long-time friend of the former governor said in a phone interview that it makes no sense attacking a rival who is more verbally dexterous than Bush.

"In retrospect it looks [foolish],” the mega-donor said. “Rubio is very articulate, got a nice style about him, what can I say." 

Said another Bush donor who spoke on condition of anonymity to avoid alienating the Bush family, “I hope they fire whoever told [Bush] to go after Rubio in the debate.” He added that he was unhappy about the personal nature of the attacks in the PowerPoint presentation. 

Another top Bush fundraiser said of the fresh round of Rubio attacks: “I don’t think it’s a wise course of action, to be frank.” 

Launching personal attacks are not in Bush’s “nature or temperament or his style,” he added. 

“Don’t go for the kill unless you know how to kill and succeed.”

But several prominent Bush donors and bundlers — lobbyists who collect money for campaign from their friends and colleagues — say the Bush team is finally making a distinction between the two that needs to be made. It’s nothing personal, they say.

"There's no ill will to anyone,” said Al Cardenas, one of Bush’s most significant and longtime supporters, in a phone interview on Friday. 

“That's not what the governor is about... It's nothing personal; it's all about providing voters with the information they need to make the right choice."

Asked why the Bush campaign was focusing on Rubio and nobody particularly else in the PowerPoint presentation, Cardenas said that it was simply a matter of strategy and timing.

"This campaign is shaping up in two lanes," he said. 

"They are not philosophical lanes, they are tone lanes. I call one the problem-makers lane and the other the problem-solvers lane... Mr. Rubio happens to be more in our lane so we will probably be dealing with these contrasts sooner with him."

The Atlanta-based Bush fundraiser Eric Tanenblatt insists there is no deep animosity to the Rubio attacks, and says they are simply educating voters on the record of Bush’s opponent. 

"I think it's fair to allow people to see the record of all the candidates," Tanenblatt said. "Any of the conversations that I've had with Governor Bush about Marco Rubio have been very positive and complimentary. Remember, Governor Bush is, was, a mentor to Senator Rubio."

Major Bush donor and family friend Mel Sembler contends that Rubio was "probably one of the weakest" speakers of the House in Florida. 

"But he could go make a speech and make everybody cry," said Sembler, appointed an ambassador to Australia by Bush’s father and to Italy by Bush’s brother. 

"I like [Rubio] personally and he's very articulate," he added, "but I want somebody with experience."

The Bush campaign and super-PAC Right to Rise suggest they will double down on the anti-Rubio strategy — a plan advocated enthusiastically by campaign manager Danny Diaz.

The campaign also denies that its PowerPoint raising questions about “Marco’s background” is a reference to the vetting process undertook by 2012 Republican presidential nominee Mitt Romney, when Rubio was on his short list to be his vice-presidential running mate. 

U.S. News reported an anonymous Bush aide said Romney’s campaign had discovered information about Rubio that concerned them. 

The woman who ran Romney’s VP vetting process, Beth Myers, strongly denied that there was anything disqualifying in Rubio’s background. 

"As the senior Romney advisor who handled VP vetting and had access to all the vetting documents, I can say that Senator Rubio "passed" our vetting and we found nothing that disqualified him from serving as VP,” Myers wrote in an email to The Hill. Paul Lindsay, a spokesman for the Right to Rise super-PAC — which has banked more than $100 million to spend promoting Bush and attacking his opponents — said the group had not heard “from a single donor” who was unhappy about the new tougher stance against Rubio. 

“Nominees should be vetted,” Lindsay said.