An electromagnetic switch for the starter of a heat engine, including a first terminal (B1), a second terminal (B2), a first mobile contact (C1) which is movable between an inactive position and a power supply position, and at least one second mobile contact (C2), which is placed between the first mobile contact (C1) and the second terminal (B2) and which is movable between a disconnected position and a connected position. The switch is capable of being placed in three operating states: an inactive state, an engagement state, and a power supply state.