diff --git a/addons/majority_judgment/MajorityJudgmentPoll.gd b/addons/majority_judgment/MajorityJudgmentPoll.gd
index 2d65a47..ef7894d 100644
--- a/addons/majority_judgment/MajorityJudgmentPoll.gd
+++ b/addons/majority_judgment/MajorityJudgmentPoll.gd
@@ -38,6 +38,8 @@ export(Array, Resource) var candidates:Array setget set_candidates, get_candidat
 
 
 # Array of MajorityJudgmentJudgments
+# If you mutate this property directly and not through add_judgment(),
+# remember to update the memoization cache as well with update_participants_index()
 export(Array, Resource) var judgments:Array setget set_judgments, get_judgments
 
 
@@ -115,6 +117,9 @@ func set_judgments(__judgments:Array) -> void:
 func add_judgment(judgment:MajorityJudgmentJudgment) -> void:
 	if not judgments:
 		judgments = Array()
+	if not judgment.candidate in self.candidates:
+		printerr("Judgment Candidate is not in the Poll!")
+		return
 	for i in range(judgments.size()):
 		var existing_judgment = judgments[i]
 		if (
@@ -124,6 +129,7 @@ func add_judgment(judgment:MajorityJudgmentJudgment) -> void:
 			):
 			judgments[i] = judgment
 			return
+	update_participants_index(judgment.participant)
 	judgments.append(judgment)
 
 
@@ -159,6 +165,42 @@ func tally() -> MajorityJudgmentPollTally:
 	return tallier.tally(self)
 
 
+func get_or_create_participant(identifier:String) -> MajorityJudgmentParticipant:
+	var known_participants = get_participants_index()
+	if not known_participants.has(identifier):
+		known_participants[identifier] = MajorityJudgmentParticipant.make(identifier)
+	return known_participants[identifier]
+
+
+# Memoization of expensive computation
+var __participants_index := Dictionary()  # id => Participant
+
+
+func get_participants_index():
+	if __participants_index.empty():
+		rebuild_participants_index()
+	return __participants_index
+
+
+func rebuild_participants_index():
+	for participant in get_participants():
+		assert(
+			not __participants_index.has(participant.name),
+			"Participants index should be consistent: names should be unique."
+		)
+		__participants_index[participant.name] = participant
+
+
+func update_participants_index(participant:MajorityJudgmentParticipant):
+	var identifier = participant.name
+	if not __participants_index.has(identifier):
+		__participants_index[identifier] = participant
+	assert(
+		__participants_index[identifier] == participant,
+		"Participants index should be consistent."
+	)
+
+
 func get_participants() -> Array:
 	var participants := Array()
 	for judgment in judgments: