A state wide caucus will meet January 15 to vote on endorsement of a Democratic presidential candidate.

The Massachusetts Citizens Presidential Caucus, sponsored by Massachusetts Action for Peace and Citizens for Participation Politics, will be held at Assumption College in Worcester. All voters eligible in the Massachusetts primary on April 25 will be able to participate in the caucus, a spokesman said.

Although the caucus has not yet sent out invitations to the candidates, Eugene McCarthy has already volunteered to attend, Robert A. Schaeffer, a member of the caucus planning committee, said yesterday.

McCarthy has agreed to withdraw from the Massachusetts primary if he does not win the caucus's endorsement, Schaeffer said, because he thinks such a move is necessary to prevent fragmentation.

Los Angeles Mayor Samuel Yorty also has volunteered to come to the caucus, Schaeffer said, but Senator Edward M. Kennedy '54 (D.-Mass.) has refused to participate. Rep. Robert Drinan (D.-Mass.) will be the caucus keynote speaker.