As for population, I am fairly sure Tolkien says in the letters that there were more Gondorian speakers of Sindarin than Elvish ones at hte time of the War of the Ring (though I think he may not have included the Silvan Elves of Mirkwood in the equation). Of course not all Gondorians would have necessarily spoken Elvish but it is a reminder of how small the populations of the Elven habitations were. Rivendell is a household - albeit a fairly substantial one. Lindon had shrunk to presumably a small community at the Havens. I can't recall any indication that they could have raised much in the way of a military force. Naturally some of the residents of Imladris were high level warriors but in quantity not so significant.
The Shire despite it's feudal fringes is the nearest you get to a democracy in ME. Most other places are ruled by hereditary leaders or those who have taken power by force - The Master of lake town may have been elected but was replaced by the scion of the Lord of Dale....
With Sam's ascendancy and social mobility, the Shire becomes more meritocratic... but otherwise Tolkien has few identifiable republican leanings...
Actually, they'll all vote for Tom Bombadil.
But would he be
boverred? ..
Art imitates life ........