Sforno on Genesis 26:10/ספורנו על בראשית כ״ו:י׳

1כמעט שכב אחד העם, the person described here as אחד העם, a euphemistic expression, was the king himself, who was after all, אחד העם, in a unique position compared to the common people. He had considered himself above the law doing whatever he pleased; or he had imagined that seeing that he was the king no one would dream of refusing to sleep with him, on the contrary every woman would be pleased to have been chosen for such an experience and that Yitzchok would be highly honoured to have his sister marry the king.

2והבאת עלינו אשם, by misrepresenting who Rivkah was, you, Yitzchok, almost made us guilty of a sin, for if the outstanding citizen of this land would have taken her, this would have caused also his subjects to be punished. This is the reason why he said: עלינו, “upon us,” instead of עליו, “upon himself.”