A theoretical concept for phase segregation of polymers in the presence of multicomponent selective solvents is presented. Phase separation is caused by nonspecific attractive interactions between the polymers and a smaller component in the solution instead of repulsion between monomers and solvent molecules. We call the component that adsorbs on the polymers and thus causes condensation "gluonic". It is shown that a discontinuous phase transition from a diluted or semidiluted state to the condensed state takes place if the fraction of the gluonic component is increased. The location of the phase coexistence can be shifted by influencing the binding efficiency of the gluonic component. This can be achieved by adding a regulator component to the solution. The latter is assumed to bind specifically to the polymer and interferes with the gluonic component. In this way a switching of the state of the polymer from dissolved to condensed can be achieved without changing the chemical properties of the system. Applications of this model range from co-nonsolvency in synthetic polymers, over polymer-nanoparticle systems, to biological systems such as the formation of protein-RNA droplets.