Copolymer containing a) 0.1 to 99.4 mol%, preferably 15.0 to 84.5 mol% and more preferably 23.0 to 79.0 mol% of one or more cationic structural units, b) 0.4 to 4.5 mol%, preferably 0.5 to 4.4 mol% and more preferably 1.0 to 4.4 mol% of one or more macromonomeric structural units and c) one or more structural units other than the structural units and, preferably 0.1 to 99.4 mol%, more preferably 15.0 to 84.5 mol% and especially preferably 20.0 to 74.0 mol% of the one or more structural units, where the one or more structural units is/are represented by the following general formulae and/or: in which R 1 and R 1a are each the same or different and are each independently hydrogen and/or a methyl radical, R 1b, R 3, R 4 and R 5 are each the same or different and are each independently represented by hydrogen, an aliphatic hydrocarbyl radical having 1 to 20 and preferably 1 to 4 carbon atoms, a cycloaliphatic hydrocarbyl radical having 5 to 20 and preferably 5 to 8 carbon atoms, an aryl radical having 6 to 14 carbon atoms and/or polyethylene glycol, are preferably each the same or different and are each independently represented by hydrogen and/or methyl and are more preferably each methyl, Y is the same or different and is represented by oxygen, NH and/or NR 3, V is the same or different and is represented by -(CH 2) x -, x is the same or different and is represented by an integer from 1 to 6, X and X 1 are each the same or different and are each independently represented by a halogen atom, C 1 - to C 4 -alkylsulfate and/or C 1 - to C 4 -alkylsulfonate, the one or more macromonomeric structural units are represented by the formula: in which R x is the same or different and is represented by H and/or methyl, Z is the same or different and is represented by C=O and/or O(CH 2) 4 and is preferably O(CH 2) 4, 1 on molar average is a number from 0 to 7 and preferably from 0 to 6, and p on molar average is a number from 1 to 150, preferably from 11 to 150 and more preferably from 12 to 150, where, when Z is C=O, R x is the same or different and is represented by H and/or methyl, 1 on molar average is a number from 1 qto 7, preferably from 2 to 6 and more preferably from 3 to 6, and p on molar average is a number from 1 to 150, preferably from 11 to 150 and more preferably from 12 to 150, and the one or more structural units is/are the polymerization product of at least one monomer species selected from the group consisting of noncationic acrylamides, noncationic methacrylamides and N-vinyl-substituted lactams having 5 to 7 ring atoms. a) 0.1 to 99.4 mol%, preferably 15.0 to 84.5 mol% and more preferably 23.0 to 79.0 mol% of one or more cationic structural units, b) 0.4 to 4.5 mol%, preferably 0.5 to 4.4 mol% and more preferably 1.0 to 4.4 mol% of one or more macromonomeric structural units and c) one or more structural units other than the structural units and, preferably 0.1 to 99.4 mol%, more preferably 15.0 to 84.5 mol% and especially preferably 20.0 to 74.0 mol% of the one or more structural units, R 1 and R 1a are each the same or different and are each independently hydrogen and/or a methyl radical, R 1b, R 3, R 4 and R 5 are each the same or different and are each independently represented by hydrogen, an aliphatic hydrocarbyl radical having 1 to 20 and preferably 1 to 4 carbon atoms, a cycloaliphatic hydrocarbyl radical having 5 to 20 and preferably 5 to 8 carbon atoms, an aryl radical having 6 to 14 carbon atoms and/or polyethylene glycol, are preferably each the same or different and are each independently represented by hydrogen and/or methyl and are more preferably each methyl, Y is the same or different and is represented by oxygen, NH and/or NR 3, V is the same or different and is represented by -(CH 2) x -, x is the same or different and is represented by an integer from 1 to 6, X and X 1 are each the same or different and are each independently represented by a halogen atom, C 1 - to C 4 -alkylsulfate and/or C 1 - to C 4 -alkylsulfonate, the one or more macromonomeric structural units are represented by the formula: R x is the same or different and is represented by H and/or methyl, Z is the same or different and is represented by C=O and/or O(CH 2) 4 and is preferably O(CH 2) 4, 1 on molar average is a number from 0 to 7 and preferably from 0 to 6, and p on molar average is a number from 1 to 150, preferably from 11 to 150 and more preferably from 12 to 150, where, when Z is C=O, R x is the same or different and is represented by H and/or methyl, 1 on molar average is a number from 1 qto 7, preferably from 2 to 6 and more preferably from 3 to 6, and p on molar average is a number from 1 to 150, preferably from 11 to 150 and more preferably from 12 to 150, and the one or more structural units is/are the polymerization product of at least one monomer species selected from the group consisting of noncationic acrylamides, noncationic methacrylamides and N-vinyl-substituted lactams having 5 to 7 ring atoms.