My experience is that it's far less than half.
When you get right down to brass tacks you're probably right, Golem.
The rest are just Republicans who vote for Republicans and rationalize that any Republican is better than any Democrat.
There seem to be very few, like you, who will actually withhold their vote from the Republican nominee and fewer yet who will vote for Clinton.
We, on the left, see him as a monster; dangerous, unpredictable, and a threat to the American way of life. Republicans see Hillary much the same way.
I don't think any of us will stand up in favor of
illegal immigration. We need immigration reform, not massive deportations or walls. Most illegals are here because they overstayed their visas. Rather than deport them we need to extend their visas. If they are criminals, they need to be jailed or exported. If they are parents of children who are citizens and want to stay here, they need a path to citizenship. There are simple ways to work this all out but as long as racism is an issue and as long as Republicans resist any path forward it's just going to remain a problem.
