WEST PALM BEACH, Fla. — Three weeks and a day after he watched his team win its sixth Super Bowl championship, Robert K. Kraft was formally charged with two counts of soliciting prostitution.

Mr. Kraft, who lives in Massachusetts but has owned property in Palm Beach, Fla., for a number of years, was one of 25 men caught in a sting operation at a spa called Orchids of Asia, a small storefront business in a strip mall in Jupiter, Fla.

On Friday, Jupiter police filed two second-degree charges against Mr. Kraft, but State Attorney Dave Aronberg of Palm Beach County increased the severity of the charges to two first-degree misdemeanors. If convicted, Mr. Kraft could face up to a year in jail, a $5,000 fine and 100 hours of community service, Mr. Aronberg said. He added that it was unlikely a first-time offender would spend time in jail.

“Human trafficking is evil in our midst,” Mr. Aronberg said. “It is fueled on the demand side.”

The charges are the latest crisis for the Patriots and Mr. Kraft, who is one of the N.F.L.’s most powerful owners, a trustee emeritus and longtime benefactor of Columbia University and a friend of President Trump’s. Mr. Aronberg made it clear that Mr. Kraft would not receive special treatment because of his prominence.