Md. Code, Election Law § 13–209

(a) Two or more candidates who have established separate campaign finance entities may form a slate.

(b) After establishing a campaign finance entity in accordance with § 13–202(c) of this subtitle, a candidate may join a slate.

(c) (1) To join a slate, a candidate shall file a written notice with the State Board.

(2) The notice shall specify:

(i) the name of the slate that the candidate has joined; and

(ii) the date on which the candidate joined the slate.

(d) A candidate may join a slate or continue as a member of a slate only if:

(1) the candidate has filed a certificate of candidacy; or

(2) (i) the candidate is an incumbent officeholder; and

(ii) the deadline for filing a certificate of candidacy for the office the candidate holds has not passed.