Republican presidential candidate Donald Trump takes part in the presidential debates at the Reagan Library on Sept. 16, 2015, in Simi Valley, California. Sen. Marco Rubio said Thursday he enjoys watching Trump's campaign unfold. Justin Sullivan/Getty Images

Florida Sen. Marco Rubio admitted Thursday that he, like the rest of the world, enjoys watching to see what fellow Republican presidential candidate Donald Trump will do next. He told a WHDH reporter that his campaign responds to Trump’s attacks “because it’s fun to watch him blow up even more.”

Trump and Rubio have been exchanging attacks for weeks since the second GOP presidential debate in September. The New York billionaire started the feud by criticizing Rubio’s poor attendance record in the Senate and saying the Florida senator sweated too much.

Rubio has missed more votes in the Senate than any other candidate running for president. But he has defended his record, saying he's not ignoring his constituents, just doing what he has to do to run for president.

"My ambitions aren't for me; my ambitions are for the country and Florida. And that's why I'm running for president," Rubio said on the "Today" show earlier this week.

The Florida senator initially said he wanted to avoid Trump’s rhetoric, but he has recently taken to responding when Trump lashes out. In recent weeks as Rubio's standing in the polls has risen, he has hit back at Trump -- and other candidates -- plenty of times. Rubio now ranks fourth among Republican primary candidates at nearly 10 percent in the Real Clear Politics polling average, while Trump remains the frontrunner with 23 percent. Rubio has called Trump a “touchy and insecure guy” and called out the businessman for not focusing on specific policy issues.

The WHDH reporter asked Rubio Thursday about a since-deleted ad that Trump had posted to Twitter calling Rubio a “nice boy” and “little RUBE.”

“This is how he gets attention,” Rubio told the reporter. Newsmax reported that Trump said his ad, which was headlined “Never Hire A Boy To Do A Man’s Job,” was “payback.”

“He’s a guy that’s sensitive to criticism and so he reacts these ways and so it is what it is,” Rubio said in the WHDH interview.