It's not exactly electrical or intra/inter-molecular forces as you conjecture in your question. Rather, it's ultimately exchange forces, e.g., https://en.wikipedia.org/wiki/Exchange_interaction. As two macroscopic objects get close (really close) together, the electron shells surrounding their respective atoms begin to affect each other. And two electrons (because they're fermions) can't simultaneously occupy the same state (be in "the same place at the same time", colloquially).
So as you try to push the macroscopic objects together, thus forcing too many electrons into the available atomic shell states, the overall multi-particle state describing that collection of electrons (determined by the Slater determinant, e.g., https://en.wikipedia.org/wiki/Slater_determinant) necessarily gives zero probability for finding any two electrons in the same state. And that gives rise to the macroscopic effect/semblance of a "force", preventing the macroscopic objects from being "in the same place at the same time".