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The covariant spectator formalism is used to model the nucleon and the$\Delta$(1232) as a system of three constituent quarks with their ownelectromagnetic structure. The definition of the ``fixed-axis'' polarizationstates for the diquark emitted from the initial state vertex and absorbed intothe final state vertex is discussed. The helicity sum over those states isevaluated and seen to be covariant. Using this approach, all fourelectromagnetic form factors of the nucleon, together with the {\it magnetic}form factor, $G_M^*$, for the $\gamma N \to \Delta$ transition, can bedescribed using manifestly covariant nucleon and $\Delta$ wave functions with{\it zero} orbital angular momentum $L$, but a successful description of$G_M^*$ near $Q^2=0$ requires the addition of a pion cloud term not included inthe class of valence quark models considered here. We also show that the pure$S$-wave model gives electric, $G_E^*$, and coulomb, $G^*_C$, transition formfactors that are identically zero, showing that these form factors aresensitive to wave function components with $L>0$.

A Covariant model for the nucleon and the $\Delta$