After the 2010 midterm elections, 19 states passed laws that put up barriers to voting, including new photo-ID and proof of citizenship requirements, and restrictions on early and absentee voting. Long lines, exacerbated by a law that reduced the number of days for early voting, discouraged about 50 thousand voters in central Florida from voting, most of them Democrats.  According to the Brennan Center for Justice, as many as five million votes might have been lost in the 2012 national election, which was, as it happens, almost exactly President Obama’s popular vote margin over Mitt Romney.
The major new target of those who want to suppress the vote for partisan political advantage is Section 5 of the Voting Rights Act. Section 5 applies to most counties in nine Southern states and a handful of counties in the rest of the country, all of which have histories of discriminatory voting practices.  Judge David Tatel, of the Court of Appeals for the D.C. Circuit, found that Section 5, far form being obsolete, continues to single out the jurisdictions in which discrimination is concentrated. As Jeffrey Toobin writes: “It (the Voting Rights Act) established a principle that voting district lines must be drawn so that African-American politicians have some chance of winning federal and state offices. But, in the South, in recent years, the Republican Party, which is dominant and, for the most part, white, has benefitted from concentrations of black voters in just a handful of districts.” 
A major unintended consequence of the Voting Rights Act is that it has been manipulated into reducing Democratic Party representation in Congress and state legislative bodies and governorships. Thus, even though Democratic cnadidates for the U.S. House garnered more than one million votes — maybe 1.4 million more — the Republican Party won 33 more House seats.
 Jeffrey Toobin, “Casting Votes,” The New Yorker, January 14, 2013.