Some experts say the incidents cited by a critic are modest and may not reflect an intentional effort to take credit. Vice President Kamala Harris’s campaign Tuesday rejected claims that she and a co-author had plagiarized a handful of passages in a 2009 book on fighting crime, arguing that the allegations amounted to a partisan attempt to weaponize a 15-year-old work. The claims arose this week when Christopher Rufo, a conservative activist, listed five instances in the book, “Smart on Crime: A Career Prosecutor’s Plan to Make Us Safer,” saying Harris and co-author Joan O’C. Hamilton used language that was...