A liquid laundry additive, comprising: a cleaning booster polymer, comprising: 60 to 95 wt%, based on dry weight of the cleaning booster polymer, of structural units of a monoethylenically unsaturated carboxylic acid monomer; 5 to 40 wt%, based on dry weight of the cleaning booster polymer, of structural units of an ethylenically unsaturated monomer of formula wherein X is selected from the group consisting of an oxygen atom and a sulfur atom; wherein R 1 is a C 2-4 alkylene group; wherein R 2 is selected from the group consisting of a 2-(2-carboxyacrylamide)ethyl group, a vinyl group, an allyl group, an isopropenyl group, an acryloyl group, a methacryloyl group, a 2-hydroxy-3-(allyloxy)propyl group and a functional group of formula R 4 -Y-R 3 - wherein R 3 is a C 1-5 alkylene group; wherein Y is selected from the group consisting of an -O- and an -NR 5 -, where R 5 is selected from the group consisting of a hydrogen and a C 1-8 alkyl group; and wherein R 4 is selected from the group consisting of a 2-hydroxy-3-(allyloxy)propyl group, a vinyl group, a methacryloyl group, an acryloyl group and a methacryloyloxyaceto group; 0 to 20 wt%, based on dry weight of the cleaning booster polymer, of structural units of an ethylenically unsaturated monomer of formula wherein A is selected from the group consisting of an -O- and an -NR 5 -; wherein each R 6 is independently selected from the group consisting of a -CH 2 CH 2 O- group, a -CH 2 CH(CH 3)O- group and a -CH 2 CH(CH 2 CH 3)O- group; and wherein b is 2 to 20; 0 to 5 wt%, based on dry weight of the cleaning booster polymer, of structural units of an ethylenically unsaturated monomer of formula wherein each R 7 is independently selected from a -C 1-4 alkyl group; and wherein each R 8 is independently selected from the group consisting of a hydrogen and a methyl group. 60 to 95 wt%, based on dry weight of the cleaning booster polymer, of structural units of a monoethylenically unsaturated carboxylic acid monomer; 5 to 40 wt%, based on dry weight of the cleaning booster polymer, of structural units of an ethylenically unsaturated monomer of formula wherein X is selected from the group consisting of an oxygen atom and a sulfur atom; wherein R 1 is a C 2-4 alkylene group; wherein R 2 is selected from the group consisting of a 2-(2-carboxyacrylamide)ethyl group, a vinyl group, an allyl group, an isopropenyl group, an acryloyl group, a methacryloyl group, a 2-hydroxy-3-(allyloxy)propyl group and a functional group of formula R 4 -Y-R 3 - wherein R 3 is a C 1-5 alkylene group; wherein Y is selected from the group consisting of an -O- and an -NR 5 -, where R 5 is selected from the group consisting of a hydrogen and a C 1-8 alkyl group; and wherein R 4 is selected from the group consisting of a 2-hydroxy-3-(allyloxy)propyl group, a vinyl group, a methacryloyl group, an acryloyl group and a methacryloyloxyaceto group; wherein X is selected from the group consisting of an oxygen atom and a sulfur atom; wherein R 1 is a C 2-4 alkylene group; wherein R 2 is selected from the group consisting of a 2-(2-carboxyacrylamide)ethyl group, a vinyl group, an allyl group, an isopropenyl group, an acryloyl group, a methacryloyl group, a 2-hydroxy-3-(allyloxy)propyl group and a functional group of formula R 4 -Y-R 3 - wherein R 3 is a C 1-5 alkylene group; wherein Y is selected from the group consisting of an -O- and an -NR 5 -, where R 5 is selected from the group consisting of a hydrogen and a C 1-8 alkyl group; and wherein R 4 is selected from the group consisting of a 2-hydroxy-3-(allyloxy)propyl group, a vinyl group, a methacryloyl group, an acryloyl group and a methacryloyloxyaceto group; 0 to 20 wt%, based on dry weight of the cleaning booster polymer, of structural units of an ethylenically unsaturated monomer of formula wherein A is selected from the group consisting of an -O- and an -NR 5 -; wherein each R 6 is independently selected from the group consisting of a -CH 2 CH 2 O- group, a -CH 2 CH(CH 3)O- group and a -CH 2 CH(CH 2 CH 3)O- group; and wherein b is 2 to 20; wherein A is selected from the group consisting of an -O- and an -NR 5 -; wherein each R 6 is independently selected from the group consisting of a -CH 2 CH 2 O- group, a -CH 2 CH(CH 3)O- group and a -CH 2 CH(CH 2 CH 3)O- group; and wherein b is 2 to 20; 0 to 5 wt%, based on dry weight of the cleaning booster polymer, of structural units of an ethylenically unsaturated monomer of formula wherein each R 7 is independently selected from a -C 1-4 alkyl group; and wherein each R 8 is independently selected from the group consisting of a hydrogen and a methyl group. wherein each R 7 is independently selected from a -C 1-4 alkyl group; and wherein each R 8 is independently selected from the group consisting of a hydrogen and a methyl group.