Republican U.S. presidential candidate Trump speaks as Rubio and Carson listen at the 2016 U.S. Republican presidential candidates debate held by CNBC in Boulder Thomson Reuters Donald Trump seems to want in on the escalating feud between Sen. Marco Rubio (R-Florida) and former Florida Gov. Jeb Bush (R).

In an early-Sunday morning tweet-storm, a tactic that's become a hallmark of his campaign for president, Trump weighed in Rubio and Bush's relationship.

He offered an opinion that neither candidate likes the other. And he said that the bitterness between the two candidates highlights both campaigns' weaknesses.

First, Trump went after Rubio, criticizing the senator for his role in helping to craft the 2013 bipartisan comprehensive immigration reform bill that ultimately stalled in Congress.

Two hours later, Trump was back. He turned his attention to Bush and said he believes Rubio and Bush don't seem to see eye to eye, despite the fact that both candidates have said publicly that they maintain a large amount of respect for one another.

Finally, Trump finished off by opining that Bush's attempt to criticize Rubio's Senate-attendance record demonstrated both campaigns' weaknesses.

Over the past week, the battle between the Bush and Rubio campaigns has spilled out into the open.

Last week, a slideshow from a Bush campaign presentation to donors showed it criticizing Rubio as a "GOP Obama." In the slideshow, the Bush campaign laid out reasons it believes Rubio is a vulnerable candidate. Several Bush donors are also reportedly being heavily wooed by Rubio's camp as the former governor's poll numbers continue to slide.

For his part, Rubio has also taken veiled shots at the Bush campaign.

"I know there are people running that have more experience than I do on the issues we faced 17 years ago," Rubio said during an interview on "Face The Nation" Sunday, referencing the year that Bush was first elected as Florida's governor. "But on the issues before America today, that's what we should be debating. And I just don't believe there's anyone else running who has a better understanding of the issues before us now than I do."