The present invention is a composition comprising a) a stable aqueous dispersion of polymer particles functionalized with structural units of a phosphorus acid monomer or a salt thereof and; b) a water-soluble polymer functionalized with structural units of a sulfonic acid monomer or a salt thereof as well as a method comprising mixing the stable aqueous dispersion of the phosphorus acid functionalized polymer particles with the sulfonic acid functionalized polymer, and TiO2. The composition of the present invention is useful as a coatings formulation that provides improved hiding over phosphorus acid functionalized binders that do not include the water-soluble polymer. Alternatively, the same hiding benefit is seen at lower phosphorus acid concentration when the sulfonic acid functionalized polymer is present.