Republican presidential candidate Donald Trump speaks to supporters at his primary election night event at his Mar-a-Lago Club in Palm Beach, Fla., March 15, 2016. At left is his campaign manager Corey Lewandowski.
Republican presidential candidate Donald Trump speaks to supporters at his primary election night event at his Mar-a-Lago Club in Palm Beach, Fla., March 15, 2016. At left is his campaign manager Corey Lewandowski.

A prosecutor in the U.S. state of Florida dropped a battery charge Thursday against the campaign manager for the Republican presidential front-runner, real estate mogul Donald Trump.

Prosecutor David Aronberg said there was "probable cause" to arrest Trump's top political aide, Corey Lewandowski, for roughly grabbing a reporter by the arm at the end of a campaign rally in early March as she approached the candidate to ask a question.

But the prosecutor, in a court filing, said "the evidence cannot prove all legally required elements of the crime alleged and is insufficient to support a criminal prosecution."

Aronberg told a news conference that Lewandowski "has a reasonable hypothesis of innocence," including that he was trying to protect Trump after the reporter brushed up against Trump or touched Trump's arm.

The reporter, Michelle Fields, then working for Breitbart News, an Internet political site, sustained bruising on one arm from Lewandowski grabbing her, and she filed a complaint with police.

Both Lewandowski and Trump disputed the circumstances surrounding the incident, but police charged Lewandowski.