Is the much-cited quote from Benjamin Rush genuine? I've never seen a citation for it.

Neither has the Benjamin Rush wiki. They do make note of it.

I've seen no quick evidence of it either at Teaching American History or Avalon Project, not that it can't be true, but such words would have quickly made it into a proper citation due to the nature of their content. It may be like the '200 year lifespan of democracy' quotation: apparently of 20th century vintage but attributed to those further back in time to give it more weight.

That does not make it an invalid view, however, just that the actual author by not having proper source citation tends to make it seem better than it is. If it is a viewpoint, then own up to it and back it without resorting to getting some 'historical authenticity'.

There is always, of course, the historical name mix-up problem, too, like the misplaced quotes of Andrew Jackson and Andrew Johnson - there are many similar ideas held between the two, but disentangling them can be a problem as even old sources (like Bartlett's) can get the citation wrong. That plus attributing later words, like above, to those in the past needs some heavy work to just get the older reference works digitized. Why the entirety of the Congressional Record has *not* been put on a fast-track is beyond me... it is the public record of the Nation and should be easily available to every citizen. Those sources doing that, TAH, Avalon, Gutenberg, Constitution.org, etc. are doing a valued public service giving us access to documents that might otherwise sit on shelves waiting for decades to be digitized. Really, getting the e-text for a few works, like Vattel's, has pushed me to buy a used copy from 1911. If Baen books can teach anything, its that e-text sells books!