The Imperial Empire as a common example in this thread, was indeed mostly successful.
As many noted, unification is impossible with the bad blood in race relations. Too much racism and hate. That is more reason for unification, imo.

However, the only way for that to ever work was how the Imperials did it, through force.
If you can use force and conquer Tamriel, forcing everyones hand into cooperation, than unification is possible.

I chose other because I think that unification through military means, for most of Tamriel is in the other category?

I think the polls spirit is that the unification choice is voluntary unification, and I also think that a few outliers should be outside of said unified nation (e.g. Dunmer who refuse to not give up slaves can have a small, almost tribal (think U.S. Native Americans) territory for themselves such as Morrowind).
Perhaps they can keep their current slaves, and children of those slaves as their "new stock", thus ending the slave trade and continued enslavement of any free peoples, while also allowing them to continue their way of life and prevent conflicts over the matter. That is an example of how to solve a problem with any 'non-unificationers', with the most difficult of them being the example.

Thoughts, fellow TES Lore-heads?

(note: I detest racism and slavery, and would personally vote to just force them all to ban slavery. However that is not diplomatic and will lead to resentment, mutiny, rebellion, etc.)

(note: I play as a Dunmer or Nord 90% of the time since I started with TESIII on Xbox.)

Always am available for private discussion with lore, the game, previous games, etc. so we don't flood the thread by going off-topic.

The Emperor will always be the person most able to seize the throne, no matter his race. And since his mother determines his race, that can change from generation to generation. The Septim line contained Nords, Dunmer, Bretons, Imperials at least. A few Empresses in there, too, which would be the only times the succession followed race, as their children would also be of theirs.

ESO has an Altmer queen in Auridon, a Breton king in Daggerfall, and a Nord king in - Mournhold?. They haven't got the memo yet. However, I note that Emeric's wife Maraya is a Redguard, so his kids will be, too. No idea if Jorunn has a wife, and Ayrenn gets to pass on her race anyway.

The central location of Imperial City makes it a desirable capital for an Empire of the entire continent, so you could argue that whoever occupies the throne there becomes an Imperial by residence, but they'd be racially random, as the game doesn't support "mixed".

Getting there is going to be mixed as well. The feudal (hierarchical) system of Emperor over lesser provincial Kings, over lesser kings of city-states will be appropriate in some places, and Great Houses will work in others. So I'm voting "other" because there won't be a single answer, even in the short term.

Tiber septim for emperor

Let's free the Peoples of Tamriel !