US lawyer Michael Avenatti, who represented porn star Stormy Daniels in her lawsuit against President Trump, has been arrested on fraud charges.
Prosecutors says he tried to extort more than $20m (£15m) from Nike, threatening to use his profile to inflict reputational harm on the firm.
In a separate case, the 48-year-old has been accused of embezzlement.
A frequent guest on TV news and talk shows, Mr Avenatti emerged as a fierce critic of Donald Trump.
At one point he said he was considering running for president himself in 2010.
Mr Avenatti appeared in a New York court on Monday and was released on $300,000 (£227,000) bail on condition that he surrender his US and Italian passports. He did not enter a plea.
Outside court, he said he was confident he would be “fully exonerated”.
He told reporters he had spent his career fighting powerful people and powerful corporations and that he would “never stop fighting that good fight”.
What are the Nike charges about?
According to federal prosecutors in New York, Mr Avenatti met a lawyer for Nike earlier this month. During their meeting, he allegedly threatened to release damaging information about the company unless it paid him and another, unnamed co-conspirator between $15m (£11.4m) and $25m (£19m).
He also demanded $1.5m (£1.13m) for an individual he claimed to represent.
Mr Avenatti reportedly threatened to take $10bn (£7.56bn) off Nike’s market value.
He was arrested in New York on Monday, shortly after announcing that he would hold a news conference about a scandal surrounding Nike on Tuesday.
“A suit and tie does not mask the fact that, at its core, this was an old-fashioned shakedown,” said prosecutor Geoffrey Berman told reporters.
Nike said in a statement it would “not be extorted or hide information that is relevant to a government investigation”.
The company said it immediately reported the matter to federal prosecutors.
What other charges is Avenatti facing?
In another case in Los Angeles, Mr Avenatti has been charged with embezzling money from a client and defrauding a bank.
Los Angeles prosecutor Nick Hanna said Mr Avenatti describes himself as an “attorney, advocate and fighter for good” on social media, while in fact he “fights for his own selfish interests”.
Prosecutors say that he negotiated a $1.6m settlement for a client, but only gave them a “bogus” agreement with a false payment date.
He allegedly then collected the settlement in secret and “advanced” $130,000 to his client, using the rest to support his “lavish lifestyle”.
Mr Avenatti is also accused of falsifying documents to secure a loan from a Mississippi bank.
He is due to appear in court in California on 1 April and in New York on 25 April.
What about Stormy Daniels?
Mr Avenatti has formerly represented Stormy Daniels, who is suing the president to get out of a non-disclosure agreement she signed before the 2016 election. The non-disclosure agreement related to an affair she said he had with Mr Trump in 2006.
On Saturday, he tweeted that the president should be indicted for colluding with his former lawyer “to violate the law and commit crimes.”
Ms Daniels, in a tweet, said on Monday that she had terminated Mr Avenatti’s contract “more than a month ago… after discovering that he had dealt with me extremely dishonestly.”
“Knowing what I know now about Michael, I’m saddened but not shocked regarding his arrest.”