The voter ID law in Wisconsin disqualified 9% of its registered voters. The right to vote is protected by 5 constitutional amendments and isn't conditional upon obtaining a state-issued photo ID. Requiring a photo ID is akin to a poll tax (24th amendment). There's no evidence that photo IDs make elections more secure, since voter-impersonation fraud is practically non-existent [0].
And that's before you get to the states which require photo ID making it somewhat more difficult by requiring it to come only from government office X which is in county Y (obviously with poor public transport) only open on every third Tuesday between 1000 and 1400.
[0] http://www.latimes.com/business/hiltzik/la-fi-mh-why-voter-i...