By Emily Stephenson and Colleen Jenkins

(Reuters) - Donald Trump's presidential campaign manager was arrested and charged with misdemeanor battery in Florida on Tuesday, the latest chapter in a raucous U.S. race marked by threats, insults and physical confrontations.

Police in Jupiter, Florida, charged Corey Lewandowski, 42, with intentionally grabbing and bruising the arm of Michelle Fields, then a reporter for the conservative news outlet Breitbart, when she tried to question Trump at a campaign event on March 8.

Republican front-runner Trump repeatedly defended Lewandowski, saying he was innocent and would fight the charges while continuing as campaign manager. Lewandowski was a good man who was "very, very seriously maligned, and I think it's very unfair," he said.

"I told him I think he should never settle this case. He should go all the way," Trump told reporters on his plane after he landed in Wisconsin for a campaign trip. "I just can't stand by and watch a man's life be destroyed."

Police released a video of the incident showing Fields walking alongside Trump and trying to question him. Lewandowski is seen grabbing her arm and pulling her backward. Previous videos of the incident had been obscured by people in the crowd.

At the time, Lewandowski called Fields "delusional" and said he never touched her.

Campaign rallies for Trump, the billionaire businessman who leads the race to become the Republican candidate in the Nov. 8 presidential election, are tumultuous at times and have been marked by occasional clashes between protesters and supporters or security personnel.

His pugnacious campaign style, which includes personal insults directed at rivals and scathing criticism of protesters, has been criticized for encouraging physical altercations at his rallies.

Trump leads rivals Ted Cruz, a U.S. senator from Texas, and Ohio Governor John Kasich in opinion polls and in the number of delegates to the nominating convention, despite a concerted effort to stop him by a Republican establishment worried he will lead the party to defeat in November.

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Cruz picked up the endorsement on Tuesday of Wisconsin Governor Scott Walker ahead of the state's primary next week. Walker, who dropped out of the presidential race last year, called Cruz a principled constitutional conservative.

"I'm all in," Walker said in a radio interview on WTMJ radio in Milwaukee, adding he was not endorsing Cruz in an attempt to stop Trump.

"I just fundamentally believe if you look at the facts, if you look at the numbers, that Ted Cruz is in the best position by far to both win the nomination of the Republican Party and to then go on and defeat Hillary Clinton in the fall this year," Walker said, referring to the Democratic front-runner.

Walker joins a number of other more establishment Republicans who have backed Cruz as an alternative to Trump, who has racked up a strong delegate lead but alienated many party leaders with his harsh views on illegal immigration, Muslims and women.

'ABUSIVE CULTURE'

Cruz told reporters while campaigning in Wisconsin that the charges against Lewandowski reflected the "abusive" culture of the Trump campaign.

"When you have a campaign that is built on personal insults, attacks and now physical violence, that has no place in our campaign, it has no place in our democracy," Cruz said. "It helps clarify for the voters what the Trump campaign is all about."

Kasich said he considered such behavior "totally and completely" inappropriate.

"If it was me, if I was in this circumstance, I would take some sort of action, either suspension or firing," Kasich told reporters in Wisconsin.

On his plane, Trump said Fields had been pursuing him after a news conference and Lewandowski was trying to "get her off me." He questioned whether Lewandowski had given Fields the bruise on her arm.

"How do you know those bruises weren't there before?" he asked reporters in Wisconsin.

Trump spokeswoman Katrina Pierson told CNN that Lewandowski would "absolutely" stay on the job.

Republican strategist Katie Packer, who runs an anti-Trump Super PAC, said the incident and the charges against Lewandowski reflected the candidate's lack of respect toward women.

"He doesn’t have the kind of values and the kind of temperament that we should expect from someone who wants to be commander in chief," she said.

Lewandowski was charged with simple battery, defined under Florida law as intentionally touching or striking a person against their will. For a first offense, it is a misdemeanor in the first degree, which carries a maximum sentence of one year in prison or a fine of $1,000.

A court date was set for May 4, according to the police report. Jupiter police said Lewandowski turned himself in, and he was issued a notice requiring him to appear in court and then released. He was not booked into the jail.

Lewandowski’s lawyer, Scott Richardson of West Palm Beach, Florida, declined to comment on whether his client would step down as campaign manager. Lewandowski will also be represented by Kendall Coffey, a Miami lawyer, the campaign said.

Fields resigned from Breitbart less than a week after the incident, citing what she said was the online news outlet's refusal to stand behind her amid the allegations.

(Reporting by Emily Stephenson in Washington and Colleen Jenkins in Winston-Salem, N.C.; Additional reporting by Doina Chiacu, Ginger Gibson, Steve Holland and Megan Cassella in Washington, and Jonathan Allen in New York; Writing by John Whitesides; Editing by Jonathan Oatis and Peter Cooney)