There is provided a strength resin polymer for papermaking that has pendant alpha-hydroxy acetal substituents to (N-alkyl)(C.sub.1-2 alkyl)acrylamide mer units. There also is provided a process for preparation of such resin polymer by adduction of a pre-existing polymer, or the monomer precursors thereto, with an acetal-aldehyde reactant under alkaline conditions. There is provided such strength resin polymer in the form of a fluid liquid system, for instance a fluid solution or a fluid oil-continuous water-in-oil emulsion, particularly when such a system has a high concentration of resin polymer. There is provided activated polymer versions of certain of such resin polymers and paper compositions containing such activated polymer. There is also provided papermaking processes including the step of activating such resin polymer.