Zwitterionic copolymers, coating compositions (e.g., aqueous coating compositions and articles containing such copolymers, and methods of coating such coating compositions; wherein the copolymer includes: (a) first monomeric units derived from monomers of Formula (I) CH2═CR1—(CO)—X—R2—[-Q-R3—]n—Y (I) or salts thereof, wherein: R1 is hydrogen or methyl; X is oxy or —NH—; R2 is an alkylene optionally including catenary oxygen; R3 is an alkylene; Q is —(CO)O—, —NR4—(CO)—NR4—, or —(CO)—NR4—; R4 is hydrogen or alkyl; n is equal to 0 or 1; and Y is phosphonic acid, phosphonate, phosphoric acid, or phosphate; and (b) second monomeric units derived from monomers of Formula (II) CH2═CR1—(CO)—X—R2—[-Q-R3—]n—[NR5R6]+—R7—Z— (II) wherein: R1 is hydrogen or methyl; X is oxy or —NH—; R2 is alkylene optionally including catenary oxygen; R3 is alkylene; Q is —(CO)O—, —NR4—(CO)—NR4—, or —(CO)—NR4-; R4 is hydrogen or alkyl; n is equal to 0 or 1; R5 and R6 are each independently an alkyl, aryl, or a combination thereof, or R5 and R6 both combine with the nitrogen to which they are both attached to form a heterocyclic ring having 3 to 7 ring members; R7 is alkylene; and Z″ is carboxylate or sulfonate. CH2═CR1—(CO)—X—R2—[-Q-R3-]n—Y  (I) CH2═CR1—(CO)—X—R2—[-Q-R3—]n—[NR5R6]+—R7—Z−  (II)