  Future galaxy surveys promise to probe local primordial non-Gaussianity at
unprecedented precision, $\sigma(f_{\rm NL}) \lesssim 1$. We study the
implications for multifield inflation by considering spectator models, where
inflation is driven by the inflaton field, but the primordial perturbations are
(partially) generated by a second, spectator field. We perform an MCMC
likelihood analysis using Planck data to study quantitative predictions for
$f_{\rm NL}$ and other observables for a range of such spectator models. We
show that models where the primordial perturbations are dominated by the
spectator field, while fine-tuned within the broader parameter space, typically
predict $f_{\rm NL}$ of order unity. Therefore, upcoming galaxy clustering
measurements will constitute a stringent test of whether or not the generation
of primordial perturbations and the accelerated expansion in the inflationary
universe are due to separate phenomena.
