GOP presidential candidate Marco Rubio fired back Tuesday against a Jeb Bush super PAC ad attacking Rubio for missing an intelligence committee hearing after the Paris terrorist attacks to instead attend a campaign fundraising event in California. 

"His attack is not accurate," Rubio said of his former mentor during a campaign stop in Iowa shortly after picking up an endorsement from Rep. Trey Gowdy, R-S.C.

"Obviously we've seen that as we get closer to election day and millions of dollars in spending have not changed his fortunes, he's become increasingly negative in his attacks,” Rubio told reporters.

Right to Rise USA, the pro-Jeb Bush super PAC that is legally barred from coordinating with Bush and his presidential campaign released the ad Tuesday morning. The super PAC is spending $1.4 million on the ad buy, which begins airing this week in the Hawkeye state.

The 30-second ad begins, "Days after the Paris attacks, senators came together for a top secret briefing threat, Marco Rubio was missing, fundraising in California. Over the last 3 years, Rubio has missed important national security hearings--- and missed more total votes than any other senator."

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https://www.youtube.com/watch?v=LoS21m1PFpM&feature=youtu.be

"I'm a member of the intelligence committee, which means a whole day before the rest of the Senate learned information, I already knew it," Rubio said in Iowa. “I had been fully briefed on it, cancelled an event to go back to D.C., in fact, on that Tuesday to be (at a) full briefing. As a member of the intelligence committee, I have access to intelligence information that isn't even shared with others who are not on the committee."

"Someone has convinced him that attacking me is going to help him win, " Rubio said, repeating a line that he used against Bush during the October CNBC debate. " He has a right to run whatever campaign he wants. "