Self-interest includes far more than any one government program. A Christian receiving welfare payments may vote Republican because of their stand on abortion. A Gun hobbits may vote Democrat because he's afraid if Republicans controlled government they would repeal Obamacare and he wouldn't able to get insurance because of his poor health. My mother always voted for the most handsome candidate. Self interest means different things to different people.Many people are surprised to learn that the poor are interested in politics and generally have rather strong opinions.Voter turnout among the poor with family income less than $40,000 is only slightly less than the 66% average of all voters.
That's surprising given the hardship of getting to the polls for many of them.
And even more surprised when those people don't consistently vote in their "self-interest".