NEW HAVEN — His cellphone started humming at 11:20 p.m. on Thursday. An urgent voice jolted Jonathan Holloway from his slumber. Students protesting racism on campus were streaming toward the home of the university’s president, the caller said.

Dr. Holloway is the first black dean of Yale College, a scholar of African-American history, and an administrator who prides himself on his close ties to his students. But the late-night march took him by surprise.

Within minutes, he was dialing Yale’s president: “You might want to get dressed.”

Over the last two weeks, Dr. Holloway has emerged as a pivotal figure here as campus demonstrations against racial discrimination have flared at Yale and around the country. The dean has embraced student demands for a more diverse faculty, a cause he has long championed, and striven to bridge the gap between the protesters and the administration.

But he has also been sharply criticized by some students who say he has failed to do enough to change the racially charged climate on campus. He and other Yale administrators have struggled to keep abreast of the fluid, fast-moving protests on campus and the heated debate on social media.