A cationic polymer obtainable by polymerization of a) at least one cationic monomer and optionally at least one nonionic monomer (monomer component a), wherein the cationic monomer according to monomer component a) in the cationic polymer is selected from a compound of the formula where R 1 is H or C 1 - C 4 - alkyl, R 2 is H or methyl, R 3 is C 1 - C 4 - alkylene, R 4, R 5 and R 6 are each independently H or C 1 - C 30 - alkyl, X is -O- or -NH- and Y is Cl; Br; I; hydrogensulfate or methosulfate, and wherein monomer component a) in the cationic polymer comprises 30 to 100 % by weight of at least one cationic monomer and 0 to 70 % by weight of at least one nonionic monomer, b) at least one crosslinker (monomer component b), c) optionally at least one chain transfer agent (monomer component c), wherein the cationic polymer has an at least bimodal molecular weight distribution with at least one first peak with an average sedimentation coefficient of ≤ 10 Sved and with at least one second peak with an average sedimentation coefficient of ≥ 10.000 Sved and the water-soluble polymer components of the cationic polymer are ≥ 25% by weight related to the total amount of cationic polymer, wherein the polymerization is carried out in two subsequent steps I) and II) with: I) polymerization of monomer component a) and monomer component b), II) polymerization of monomer component a), optionally monomer component c) and in the complete absence or in the presence of < 10 ppm (related to the total amount of polymer) of monomer component b), wherein step II) is carried out after the polymerization of step I) is finished or step I) is carried out after the polymerization of step II) is finished and wherein in step II) ≥ 25% by weight of the water-soluble polymer components of the cationic polymer are produced related to the total amount of cationic polymer. a) at least one cationic monomer and optionally at least one nonionic monomer (monomer component a), wherein the cationic monomer according to monomer component a) in the cationic polymer is selected from a compound of the formula where R 1 is H or C 1 - C 4 - alkyl, R 2 is H or methyl, R 3 is C 1 - C 4 - alkylene, R 4, R 5 and R 6 are each independently H or C 1 - C 30 - alkyl, X is -O- or -NH- and Y is Cl; Br; I; hydrogensulfate or methosulfate, and wherein monomer component a) in the cationic polymer comprises 30 to 100 % by weight of at least one cationic monomer and 0 to 70 % by weight of at least one nonionic monomer, R 1 is H or C 1 - C 4 - alkyl, R 2 is H or methyl, R 3 is C 1 - C 4 - alkylene, R 4, R 5 and R 6 are each independently H or C 1 - C 30 - alkyl, X is -O- or -NH- and Y is Cl; Br; I; hydrogensulfate or methosulfate, b) at least one crosslinker (monomer component b), c) optionally at least one chain transfer agent (monomer component c), I) polymerization of monomer component a) and monomer component b), II) polymerization of monomer component a), optionally monomer component c) and in the complete absence or in the presence of < 10 ppm (related to the total amount of polymer) of monomer component b), I) is carried out after the polymerization of step II) is finished and wherein in step II) ≥ 25% by weight of the water-soluble polymer components of the cationic polymer are produced related to the total amount of cationic polymer.