Vote suppression can be applied very selectively. Insufficient voting machines, etc. can be applied on a precinct-by-precinct basis; the GOP has already used this tactic to force delays (of several hours in some cases) for voters at specific precincts in Ohio and elsewhere. Some restrictions can be applied on a county-by-county basis. And some suppression can be done on an individual basis — minor problems with ID (e.g. whether a middle name is spelled out or replaced with initial) are, by default, at the discretion of a local official.
Also there are many seemingly non-discriminatory suppression programs which do act against specific ethnic groups. For example, due to the peculiarities of surname distribution, voter harassment/suppression programs like Crosscheck are much more likely to victimize Blacks, Chinese and Hispanics than to victimize WASP’s. The GOP suppression measures have been very cunning — we could wish they would use their intelligence for good instead of evil — and will get even more blatant under the direction of Bannon and his ilk.
And many Dopers ignore that it is not necessary to make it impossible for a likely Democrat to vote. It is enough to make the registration or voting process sufficiently onerous. American elections are often very close, and even a smidgen of suppression or harassment is likely to swing the decision.
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About the claim that voters will reject the in-party if the economy doesn’t recover: Most Trump voters are doing OK financially; complaints about economic conditions are often stirred up by propaganda. For example, some of the biggest anger against illegal immigrants came from states with very few illegals! Trump will seek tax cuts, trickle-down government graft, and pumping up the stock market, creating at least a short-term illusion of prosperity. This needs low interest rates, so I expect to see major attempts by the Trump Administration to put a muzzle on the FRB (Chairman Yellen is almost 71). The resultant inflation will be billed as an unimportant price for making America Great Again.