People on welfare somehow manage to pay for cable, beer and tobacco. A small fraction of that could easily pay for an ID. If it's a poll tax, then it sucks at being a poll tax.
And we already have a national ID, it's just not a very good one. Bars will turn you away and restaurants won't serve you alcohol if you don't have a government issued ID showing your age.
I'm not sure if voter ID will solve anything, but I find the argument that requiring people to make a trip to the DMV is "discrimination" to be overblown at best and intentionally disingenuous at worst. If you don't care enough to make it to your local DMV, I sure as hell don't want your mindless ass voting.