It wouldn't matter if the Senate whip count was stacked against him. Mr Trump is a narcissist. No Narcissist worth being called a narcissist would ever in this life or the next admit to a defeat. Mr Trump will never resign. Hell, he may not leave the WH under any circumstances.
The Democrats will have to present a case so egregious, no one could say it is just sex in the WH. Should that happen, it may persuade enough Republicans to vote their conscience and not their fealty to Mr Trump and his Base, to convict. As of now, if Mr Trump was Charles Manson, and there were tapes of him killing a family, the Senate would not convict.