In the early 2000s, as the uprising known as the second intifada instilled fear in Israelis through a series of suicide bombings, Kenneth Marcus, then an official in the U.S. Department of Education, watched with unease as pro-Palestinian protests shook college campuses.

“We were seeing, internationally, a transformation of anti-Israel animus into something that looked like possibly a new form of antisemitism,” Mr. Marcus recalled in an interview, adding that U.S. universities were at the forefront of that resurgence.

Ever since, Mr. Marcus, perhaps more than anyone, has tried to douse what he sees as a dangerous rise of campus antisemitism, often embedded in pro-Palestinian activism.

He has done it as a government insider in the Bush and Trump administrations, helping to clarify protections for Jewish students under the 1964 Civil Rights Act and broadening the definition of what can be considered antisemitic.

He has also been an outside agitator, filing and promoting federal claims of harassment of Jews that he knows will garner media attention and put pressure on college administrators, students and faculty.

The impact of his life’s work has never been more felt than in the last few months, as universities reel from accusations that they have tolerated pro-Palestinian speech and protests that have veered into antisemitism.