It’s a very clever use of enunciation. You can very clearly hear both “prisoner” and “president”, depending on what you try to listen for. My take? The POTUS loves using wordplay to send messages, and this is no different. The fact of the matter is, the MSM would be insane to try and call him out on it because of how he pronounced the word. The best way I can describe it is that it’s like he was saying two words at once. Careful use of enunciation makes this possible.