We investigate the critical behavior of a three-dimensional short-range spin glass model in the presence of an external field ǫ conjugated to the Edwards-Anderson order parameter. In the meanfield approximation this model is described by the Adam-Gibbs-DiMarzio approach for the glass transition. By Monte Carlo numerical simulations we find indications for the existence of a line of critical points in the plane (ǫ, T ) which separates two paramagnetic phases and terminates in a critical endpoint. This line of critical points appears due to the large degeneracy of metastable states present in the system (configurational entropy) and is reminiscent of the first-order phase transition present in the mean-field limit. We propose a scenario for the spin-glass transition at ǫ = 0, driven by a spinodal point present above Tc, which induces strong metastability through Griffiths singularities effects and induces the absence of a two-step shape relaxation curve characteristic of glasses.Among all different approaches to understand the glass transition the thermodynamic theory of Adam-Gibbs-Di Marzio (AGM) has deserved a lot of interest during the last decades [1]. The AGM theory predicts the occurrence, at a Kauzmann temperature T K , of a second order phase transition for the metastable undercooled liquid where the configurational entropy (also called complexity) vanishes. The validity of the AGM theory for real glasses has never been demonstrated so the correct description of the glass transition still remains open [2]. An alternative dynamical approach was proposed in the eighties to describe relaxational processes in the undercooled liquid regime, experimentally observed in scattering and dielectric measurements. This received the name of mode-coupling theory (MCT) [3].Quite recently it has been realized that spin glasses are models which account for both the thermodynamic (AGM) and the dynamical (MCT) approaches [4]. Although spin glasses are models with quenched disorder (and structural glasses are not) this is not an essential difference because the existence of a crystal phase in structural glasses has no dramatic effect in the dynamics of the (disordered) metastable undercooled liquid phase. Unfortunately, up to now this connection between spinglasses and glasses remains only at the mean-field level and it is not clear what happens if one considers shortrange interactions. In fact, concepts such as complexity in AGM or the ergodicity parameter in ideal MCT are originally mean-field and it is not clear what is their relevance in short-ranged realistic systems.Recently it has been suggested [6,5] that the effect of the complexity could be observed through numerical simulations in a generic glassy system coupling two replicas by introducing a term in the Hamiltonian of the type −ǫq (ǫ being the conjugate field of the order parameter q which is the overlap between the configurations of the two replicas [7]). Through the study of an exactly solvable spin-glass model it has been shown the existence of a first order tra...