(Reuters) - In the days since police arrested more than 100 pro-Palestinian demonstrators at Columbia University on April 18, a protest encampment has been re-established on the New York campus and hundreds of protesters have been arrested at schools from California to Massachusetts.

The protests over the conflict between Israel and Palestinians - and the response from administrators, politicians, faculty and students to the demonstrations - have roiled college campuses and divided the American public. Here is a look at some of the key players.

STUDENT GROUPS

The protests at Columbia have been organized by Columbia University Apartheid Divest (CUAD), which describes itself as a coalition of more than 100 student groups. It was founded in 2016, and unsuccessfully sought to end investments by Columbia in weapons manufacturers and other companies that support Israel's occupation of Palestinian territories.

Students, including Jewish, Muslim and Palestinian members, "reactivated" the coalition and its divestment demands after the deadly hostage-taking incursion by Hamas militants from Gaza into Israel on Oct. 7 and Israel's fierce response in the Gaza enclave controlled by Hamas.

Columbia students have organized both Muslim and Jewish prayers at the encampment, and some have given speeches condemning Israel and Zionism and praising Palestinian armed resistance.

The lead CUAD negotiator in talks with university officials is Mahmoud Khalil, a Palestinian second-year postgraduate student in Columbia's School of International and Public Affairs. Though he often stops by to speak to people at the encampment and to journalists, Khalil has not stayed at the protest camp.

Among the lead student groups in the coalition are the Columbia chapters of Jewish Voice for Peace and Students for Justice in Palestine. The two decades-old anti-Zionism advocacy groups that protest Israel's military occupation have chapters across the country that have been key to protests on other campuses.

Columbia suspended both groups in November, saying they had helped organize a protest that violated the school's events rules. The students, helped by the non-profit New York Civil Liberties Union, are suing the school, saying Columbia did not follow its own disciplinary procedures and that the punishment is disproportionate.

NEMAT MINOUCHE SHAFIK

The Egyptian-born international and public affairs professor has been president of Columbia University since last July. She was called to testify before the House Committee on Education and the Workforce about alleged antisemitism on campus on April 17. She told lawmakers: "It is distressing that some in our community have acted in a manner that is inconsistent with our values."

The following day, Shafik authorized New York police to enter her campus to clear the protest encampment. A pro-Palestinian U.S. group filed a civil rights complaint against the university over its actions.

HOUSE COMMITTEE ON EDUCATION AND THE WORKFORCE

The House of Representatives' committee and its subcommittees have held at least four hearings and events focused on student activity stemming from the conflict in Gaza, with member Elise Stefanik, a top House Republican, playing a key role.

Claudine Gay resigned as president of Harvard University and Liz Magill resigned as president of the University of Pennsylvania after being criticized for their testimony late last year before the committee. They had declined to give a definitive "yes" or "no" answer to a question by Stefanik as to whether calling for the genocide of Jews would violate their schools' codes of conduct regarding bullying and harassment, saying they had to balance it against free-speech protections.

Virginia Foxx, the panel's chair, accompanied House Speaker Mike Johnson on a visit to Columbia University on April 24, saying in remarks on campus: "Columbia University is in a freefall ... The inmates are running the asylum."

ASNA TABASSUM

The University of Southern California selected Asna Tabassum, a biomedical engineering student with a minor in resistance to genocide, to be its valedictorian. Tabassum, who is Muslim and from a South Asian family, had posted a link to a pro-Palestinian page to her Instagram account.

On April 15, the school announced it would not be allowing her to deliver the traditional speech at the school's graduation, citing security risks.

"I am both shocked by this decision and profoundly disappointed that the University is succumbing to a campaign of hate meant to silence my voice," Tabassum said in a statement.

USC announced on April 25 it would be canceling its main commencement ceremony altogether following student protests on that campus this week.

(Reporting by Makini Brice in Washington and Jonathan Allen in New York; Editing by Donna Bryson and Bill Berkrot)