I was reading every appearance of Calvin Ellis and I have noticed this:

In Final Crisis #7 we only know he is the President of the United States in his secret identity, but we don't know what's his name. Courtney is his human assistant, while Brainiac is his "computer" assistant. In Action Comics v2 #9, he discover a lot about him. As Calvin Ellis, he is the President of the United States. He is from Vathlo. His identity is secret. Then, he next appear in Justice League of America's Vibe #8 but it's just the background of a panel and then we go to Multiversity. Here the status quo seems to be the same and in the guidebook it's written that: "in his alter ego of Calvin Ellis, Superman is president of the United States of America". So, his identity is still a secret.

In Superman v4 #14 (Multiplicity part one), Clark calls him "Mr. President". It's a little strange, because they talked as they have met before but Calvin is explaining him what's Justice League Incarnate. If they have not met before, it's also very strange to have Clark calling him "president". In #15 and #16 there is not a single mention about this anymore except for one panel where Red Racer call him "Mr. President". I think it's here where the confussion starts but you could think that people in the multiverse knows Calvin is the President while his secret identity is not known in Earth-23. Then we have a pair of appearances of Superman here (Justice League v3 #33) and there (Justice League v4 annual 1) but it's one panel here, one panel there... Nothing really important until The Terrifics v1 #11 where Mr. Terrific says "This world is not all that different from my own, with the notable exception that the Superman here is also the President of the United States". It's not clear if it's identity is secret or not but it may seem so. And in The Terrifics v1 #14 is not mentioned.

Next is Dog Days of Summers #1, but the story takes place in Earth-26. The important thing to notice is that Captain Carrot calls him just "Superman" but "President Superman" is seen in a caption and Atomic Batman calls him "Mr. President". Then a lot of small appearances, mainly in Justice League (#25, #26 and later on, #34, 35 and a single panel in Tales of the Dark Universe: Teen Titans - The Judas Contract) until we get to Flash Forward #2 where we can clearly see "President Superman" written in a nameplate in the White House.

So... Did I miss an appearance where this is explained? Or it was just a mistake by Tomasi (Superman v4 #14-16) followed by the next writters (mainly Lemire and Lobdell)? Do you prefer his identity to be secret or not? I think I prefer him to be Superman and President Calvin Ellis and not President Superman, but let me know what you think.

And thanks for answering!