"As state attorney I have made the decision that this office will not be filing charges against Corey Lewandowski for battery," Aronberg said at a news conference.
Aronberg said police were within their right to charge Lewandowski, but prosecutors are held to a higher standard and thus didn't find enough to bring the case.
He also revealed that Trump personally spoke with prosecutors and the campaign shared a draft of an apology letter with Aronberg's office "earlier this week," though it apparently has not yet been sent.
Lewandowski said Thursday night he was relieved the charges were dropped and he wanted to move on from the incident, which he called a "huge distraction" for the campaign. He said he was "thankful" for Trump's loyalty.
"What we saw was, you know you have an individual that remembers an incident very differently than the way I remember it. I don't remember it at all, candidly, and my entire interaction with her was on that videotape. I've never met her before, I've never spoken with her afterward," Lewandowski told Fox News' Sean Hannity. "So my sum total of that relationship with her was about three seconds long. I know that sounds like a long time, but in a three-second incident that I don't recall because it wasn't very memorable, this has really taken over a big piece of my life. I'm glad it's behind us."
The Trump campaign released a statement Thursday calling the matter closed.
"Corey Lewandowski is gratified by the decision to drop the misdemeanor charge and appreciates the thoughtful consideration and professionalism by the Palm Beach State Attorney and his staff who carefully reviewed this matter, as well as Mr. Trump's loyalty and the support of his colleagues and family during this time," the statement said. "The matter is now concluded."
Aronberg and his deputy who reviewed the case, Adrienne Ellis, said the video clearly shows Fields making contact with Trump's arm as she tries to interview him, him recoiling and shows Lewandowski grab her arm and pull her away.
After reviewing the evidence in the case, the state attorney said he doesn't feel there is enough evidence to pursue criminal charges. He explained that while police are required to meet a "probable cause" threshold to make an arrest, prosecutors must believe they have a chance to prove beyond a reasonable doubt the battery occurred and get a conviction.
"They acted well within their authority to investigate and make an independent charging decision. We agree that probable cause exists for the Jupiter Police Department to charge Mr. Lewandwoski in this case," Aronberg said. "Our standard is higher than probable cause. ... Although the facts support the allegation that Mr. Lewandowski did grab Ms. Fields' arm against her will, Mr. Lewandowski has a reasonable hypothesis of innocence"
The news is a sigh of relief for both Lewandowski and the Trump campaign, which risked facing a major legal distraction during the heat of the competitive presidential campaign.
"I think it's justifiable what he did," Lewandowski's attorney Brad Cohen told CNN's Brooke Baldwin. Aronberg said Lewandwoski may have been protecting Trump.
The incident at Trump's Mar-a-Lago estate on March 8, the night of the Michigan presidential primary, led to a weeks-long dispute between the Trump campaign, some media outlets and Fields, as to what actually happened.
Politico first reported
that Lewandowski would not be charged.
Fields may still seek defamation charges against Lewandowski based on his efforts to dismiss her claims and cast doubt on her integrity, according to one source.
Cohen suggested on CNN that she may not want to: "I don't find it to be that good of an idea to file a defamation suit in this case because it just opens doors to your past and other things," he said.
In response to the reports the charges would be dropped, Fields tweeted: "Prosecutor's office told me they would inform me of decision tomorrow. If reports true, guess they decided to leak to reporters first. Ugly."
Earlier this week, the state attorney's office tried to broker a deal in which Lewandowski would agree to publicly apologize to Fields instead of facing prosecution, one source with knowledge of the situation said. While Fields agreed to the offer, it's not yet clear that Lewandowski did.
Aronberg confirmed that the office would have appreciated an apology and that the draft of a "short" apology letter was shared with them, but said it did not factor into their decision making.
"The apology, in a case like this, obviously would be encouraged," Aronberg said. "We always appreciate when people take responsibility for their actions."
"Would he apologize for having any contact with her? Certainly he could but I don't know," Cohen said.
Fields added: "For those asking, office of prosecutor asked 2 weeks ago if I'd be ok with an apology from Corey. I said ya but haven't heard back about it."
Aronberg also denied that any political calculations went into his decision. He is a registered Democrat and has supported Hillary Clinton, but he also noted that he shared a bathroom at law school with Texas Sen. Ted Cruz, Trump's Republican opponent, and knew former candidate Sen. Marco Rubio in Florida.
"My political affiliation and my political leanings are very public, but they don't come inside this office," Aronberg said. "The sole bearing on our decision was the facts of this case and the law"
Trump has stood by his aide, initially saying he thought the allegations were made up, but multiple videos of the encounter appeared to show Lewandowski pulling Fields' arm.
"I would have loved to have fired him," Trump told CNN's Anderson Cooper during a town hall event in March. "It would have been much easier than talking to you about this all night long ... I don't want to ruin (Lewandowski's) life."
Trump attributed Lewandowski's actions to security concerns.
"She had a pen in her hand, which Secret Service is not liking because they don't know what it is, whether it's a little bomb," he said.
Trump also forcefully rejected calls from his rivals to suspend or fire Lewandowski, saying Wednesday on ABC's "Good Morning America," that "The other candidates, they said, 'Oh, I should fire him.' That's because they're weak, ineffective people. They want to be politically correct. I don't want to be politically correct. I want to be correct."
Fields, who was a reporter for Breitbart at the time, resigned from the conservative news outlet one week later, along with other staffers.