When is a policy not a policy?

Donald Trump's waffling on immigration — which seemed at the root of his presidential campaign — has even his own campaign staff sounding confused. After months of pledging to round up and deport some 10 million people, last week he proposed what sounded like "amnesty" to some long-time supporters. Or did he?  He still wants "the wall," and he might or might not make an immigration speech Wednesday — in the interests of "clarification." If he does, how much will it matter to his base or to the rapidly diminishing number of undecided voters?