The latest round picked up steam in the wake of campaign finance reports filed this week with the Federal Election Commission, with both campaigns on Friday trading shots over which organization is the most frugal.
The fight over the money game isn't frivolous to either campaign. Both have staked much of their campaign strategy in how they manage finances, and the spat comes as Rubio's presidential campaign has picked up its poll numbers in recent weeks.
"Lying about budgets. Guess Marco picked up something in the Senate," tweeted Tim Miller, Bush's campaign spokesman, linking to a Tampa Bay Times article about the cash measure discrepancy.
He also targeted the campaign the day before, calling Rubio hypocritical for touting its penny-pinching.
"Haven't seen the Rubio press release on frugality did it include the $6 million in secret money TV ads they saved money on?" Miller tweeted
Meanwhile, Rubio deputy campaign manager Rich Beeson hit the Bush campaign for spending on private planes.
"Maybe they will brag about spending 340% more on private air charters," Beeson tweeted.
Mere minutes after Bush's camp released his fundraising numbers on Thursday, the Rubio team put out a press release touting their bigger cash on hand total.
That afternoon, Bush's team announced it raised $13.4 million in the third quarter and had $10.27 million cash on hand. Then, Rubio's campaign fired off a press release announcing that Rubio finished with more money in the bank at $10.98 million, though it raised only $5.7 million this quarter.
But when general election funds are subtracted, Rubio has $9.78 million cash to spend in the Republican primary with Bush holding slightly more at $10 million.
Bush's son also got in on the action at a New York University College Republicans event on Thursday.
"As a Floridian, I'm a little disappointed, because he's missing, like, 35% of his votes. And it's just kind of like, dude, you know, either drop out or do something, but we're paying you to do something, it ain't running for president," Jeb Bush Jr. told about 30 students, according to Politico Florida
"We're way ahead of Marco's campaign," he added. "Marco doesn't have an office in Florida."
Rubio's campaign declined to comment on either of the attacks, but his spokesman, Alex Conant, did defend Rubio's fundraising.
"Regarding our numbers, we'll let our FEC report speak for itself," Conant said. "Obviously it shows a very lean campaign that is saving a lot of money. We are on track to having the resources we need to compete in every state and win the Republican nomination."
For Bush, the strategy, as his allies have described it
, has been a "shock and awe" effort to raise eye-popping sums as a show of force.
But this week's filings were far more subdued than Bush's previous quarter and more in line with competitors, an unwelcome headline as Bush struggles to alleviate donors' concerns and catch front-runner Donald Trump and second-place Ben Carson in the polls.
On the other hand, Rubio has never had huge fundraising numbers, but his campaign has been priding itself on its frugal strategy, saving up money for the home stretch of the campaign.
'He remains a good friend'
The flare-up between the campaigns has come after months of quiet but courteous tension between two men, who have long had intertwined political careers. They describe each other as friends and Rubio was often seen as a Bush political protegee.
Trump started to call Bush and Rubio's friendship into question late last month in a speech in South Carolina, where he said it was disloyal of Rubio to run against Bush and said the two "hate each other." He repeated the attack a week later in New Hampshire.
So far, the two have publicly maintained they have stayed friends.
"He remains a good friend," Rubio told reporters last week. "I have great admiration and respect for him and affection for him as a person. I'm not running against Jeb Bush, I'm running for president. And there are other people running as well. These things will happen, it's not a big deal."
Bush responded to Trump by saying Rubio is capable of putting "his big boy pants on."
"I can take criticism. (Rubio) can as well," Bush said. "We're close friends and I admire him greatly. It's a little awkward, as I've always said, that he's running for the same spot I am, but he has every right to do it. ... Donald Trump has no knowledge about my relationship with Marco Rubio."
But in the same press availability, Bush maintained his call for lawmakers' pay to be docked if they miss votes -- of which Rubio has missed the most this year of any senator running for office. And Rubio has continued his campaign refrain of needing new blood in Washington and "21st century" ideas -- a shot at the old guard he's running against.