In the current environment, Mr. Blum has been called many things, including a courageous man of the moment willing to take on entrenched, politically correct policies, and a tool of rich conservatives trying to extinguish efforts to help historically oppressed minorities overcome the long shadow of racism.

In most of his cases, Mr. Blum either sues under the name of his own organizations, or he recruits plaintiffs to challenge racial policies he thinks are unfair. Although he claims to have 22,000 members in his group Students for Fair Admissions, the plaintiff in lawsuits against Harvard and other colleges, Harvard says in court papers that he is a gadfly whose organization is nothing but his “alter ego.”

Rachel Kleinman, senior counsel at the NAACP Legal Defense and Educational Fund, said that Mr. Blum’s opposition to affirmative action was related to “this fear of white people that their privilege is being taken away from them and given to somebody else who they see as less deserving.”

Pointing to his own upbringing and the anti-Semitism his family experienced in the South in the 1950s and ’60s, when his father was a traveling salesman and some hotels did not accept Jewish guests, Mr. Blum said such criticism missed the mark.

He recalled living in Orlando, Fla., when his family’s synagogue received a bomb threat and the congregation asked a neighboring church to join it in forming a citizen patrol. The church refused — until, Mr. Blum said, his father called a bomb threat to the church.

“I seem to come from a line of compulsive people who believe in certain things and just don’t let go of them easily,” he said, smiling.

Victory Inspired by Loss

His first lawsuit was a product of personal experience. Mr. Blum (pronounced Bloom) ran for Congress in Houston as a Republican in 1992, and lost. What bothered him most, he said, was the district’s tortured shape, designed to make it easier for a minority candidate to win the seat. He filed a case claiming racial gerrymandering and nursed it to the Supreme Court, which ruled in his favor in 1996. He began to file similar suits in other states.