ELPs constitute a particularly nice model system as they can be expressed by bacteria in a strictly monodisperse fashion with different repeating sequences. It is possible, for instance, to synthesize pentapeptide sequences of the generic form (VPGXG) n , where X stays for any amino acid except proline. One can thus easily modulate the hydrophilic, hydrophobic, and charged character of the ELPs 20 together with their LCST. Salt-specific effects were studied not only for few neutral ELPs (e.g., V-120), but also for the weakly positively charged KV 6 -120, and the weakly negatively charged DV 2 F-64. For completely neutral polymers, e.g., pure PNIPAM or neutral ELPs, only two regimes of salt action were reported in the literature, see Figure (a). (I) Linear and rather steep decrease of the cloud point temperature (an approximate but direct measure of the LCST) with salt concentration was observed for most strongly hydrated salts, such as sulfates, acetates, fluorides, and chlorides. (II) Initial weak increase of the cloud point temperature at low salt concentrations, typically below 1 m, with subsequent decrease at higher concentrations. Only recently a third regime, which was predicted by computer simulations and is characterized by strongly attractive bridging interaction, was found. Guanidinium thiocyanate, one of the most potent protein denaturants, steeply decreases the cloud point temperature below 1.5 m, and the temperature grows even more rapidly above 1.5 m salt. The relation of this to the phenomenon of cononsolvency in solvent mixtures is under discussion. Charged ELPs possess a more complex behavior due to the ion-specific screening at low salt concentrations, cf. Figure 1 (b), similar to the stability behavior of charged proteins. It is now of fundamental importance to characterize the regimes in which specific salt-effects operate. This would allow to build a predictive model, which may be applied for determination of protein stability, but also for designing biomaterials of desired properties in their native environments. Computer simulations have already illuminated the action of varying solvents and cosolutes in coarse-grained simulations or all-atom simulations. Typically the results are interpreted by theories for chain structure and swelling, 38 e.g., due to a counterion condensation at highly charged polymers or specific steric interactions. Yet, a quantitative description of ion-specific counterion condensation relies on all-atom simulations. Driven by increasing interest in cononsolvency and the action of mixed solutes on the polymer structure, a whole body of mean-field theories has been developed especially for the description of the coil-to-globule transition in mixed solvents. Recently, we have developed a thermodynamic approach for neutral polymers (such as PNIPAM, or neutral ELPs) within the framework of preferential binding, which helps interpreting the salt-specific thermodynamic fingerprints of cosolutepolymer interactions. A similar model was used and extended to include non-specific screening effects for weakly charged polymers. In this work we aim to fully understand the complex data for charged elastin (selected data shown in Figure ). For this purpose we devise a generic simulation model of a charged polymer with different charge fractions in uni-univalent salt solutions. The ion-specificity of salts steps in by systematically varying the polymer-ion interactions, i.e., from more repulsive, mimicking strongly hydrated ions (extreme 'kosmotropes'), to very attractive, mimicking weakly hydrated ions (extreme 'chaotropes'). Our previous simulations of neutral polymers exhibiting simple upper CST (UCST) have already demonstrated a non-trivial response of the polymer, where collapse by depletion, swelling through weak attraction, and re-entrant collapse by strong attractions have been observed. As indicated by experiments, the situation becomes more complex in charged systems, where screening and synergistic cation and anion interactions with the polymer are expected. In this work, we therefore complement the simulations with a new theory that extends our Flory-type mean-field model for neutral polymers with approaches for ion-specific screening.