But under what conditions does "it is time for group X to have a representative as leader" become a persuasive argument?
The most obvious case is when the office is purely honorary, and we assign it to this or that person in turn, in recognition of their accomplishments or those of the group we call on them to represent. Legislators spend a little time on school children's proposals to designate state birds, state landforms, and so on. It's part of teaching kids how government works. The outcome doesn't matter--if every state has vanilla as its state ice cream flavor, maybe it's the turn of butter pecan.
I'm not sure this is the case with the US President. Plenty of power still inheres in the office, despite the vast unaccountable bureaucracy that never stops growing. Discard this case.
With that option out of the way we come to grimmer prospect. If we rule out "it doesn't make a difference" we're left with "it makes a difference." That difference can be symbolic or substantive.
If it is symbolic, and is only done for encouragement, this implies three presuppositions--actually four.
- Said group regards itself as distinct from the rest.
- It needs encouragement.
- The symbol will effectively encourage.
- And that there is no plausible way for any of the selected group to achive that position on their own.
That sounds a bit patronizing. And notice that all four requirements are necessary but not sufficient--there can be any number of reasons why is is useful but not time right now.
On the other hand, if simple use of a symbol is going to be effective, whatever it may be that seems to separate the group must not be very dire. That can argue for or against using the symbol: "it isn't badly needed" vs "easy to fix."
The other option--that the difference is substantive--represents a very bad situation.
It means that the interests of the different groups are substantively different, and that members of one group cannot be trusted to respect the interests of any other. The reason it is the "turn" of group X is that without their turn in power they will be oppressed, and may turn violent. You can easily find examples of this sort of thing in multi-ethnic governments. Lebanon worried along with a system in which different ethnicities were assigned different positions in government--because without such a balance of power they tried to kill each other. BTW, the system broke down.
Is that what you want to say we have? Not e pluribus unum, but warring tribes? If warring tribes is what we have, that's what we have, and we must deal with it. Ugly compromises will have to be made--the US Constitution includes a few (and a clever one--the Electoral College).
I want "e pluribus unum." I want "neither Jew nor Greek." I want us "all in this together." But if we've gotten too big to hold together, I want some clarity in the discussion.