I think it is a leap to assume from this second-hand story that “you’re going to destroy my presidency” was meant in a personal sense (i.e., your opposing the healthcare plan will result in destroying my presidency which will hurt my self-esteem/feelings.) Even if the phrase was retold accurately, Obama could very well have meant this in a political sense (i.e., your oppossition to the plan will destroy my presidency and thus destroy the political goals you (supposedly) believe in.