Before he arrived in California, Mr. Buck rose to prominence in Arizona in the 1980s. He was a Republican then and led the Mecham Recall Committee, an effort to remove the Republican governor, Evan Mecham, from office. Mr. Mecham was eventually impeached, accused of fraud and perjury. Mr. Buck later became a Democrat.

After five years of modeling in Europe, Mr. Buck returned to Arizona, broke and bored, according to a 1987 column in The Arizona Republic. He bought a business from a friend that gave driver’s license information to insurance companies and told the newspaper that he changed his last name from Buckmelter to Buck. Mr. Buck bought his friend out of the business for $250,000 and then sold it in 1986 for a significant profit, he told the newspaper.

Image Mr. Buck in 2010. Credit... Damian Dovarganes/Associated Press

After his move to California, he drew attention in West Hollywood as part of a group that successfully campaigned against a plan to build affordable housing units in a city-owned building.

Questions over Mr. Buck’s source of wealth remain. In asking a court to set Mr. Buck’s bond at $4 million, prosecutors wrote that he was not employed and argued that if Mr. Buck does post bail, the court should order him to show that he did not secure any of the bond money illegally.

“He has no known source of income,” court documents said. “Yet he is able to fund his lifestyle of preying on vulnerable men. He is engaged in frequent narcotics activity, and he may be funding his lifestyle with narcotics trafficking.”

Mr. Buck was not a major Democratic donor but he handed out tens of thousands of dollars to California Democrats, including Representatives Ted Lieu, Adam B. Schiff, Pete Aguilar, Jerry McNerney and Jimmy Gomez. One recipient of larger gifts was Kyrsten Sinema, a congresswoman at the time who is now an Arizona senator. Mr. Buck also made contributions to the Democratic Congressional Campaign Committee in 2016, and to both Hillary Clinton and Barack Obama.