The real minimum wage has fallen over time due to inflation. It should be increased as part of strategy to address growing inequality. This article describes the issue in terms of its effectiveness as a campaign strategy for 2014. Polls suggest that it would appeal to a wide range of voters. It would be an effective strategy as long as Republicans oppose it. They have usually opposed most policies that interfere with the "free market", and they traditionally like to align themselves with the interests of small businesses which usually vote republican.
This may be an effective election year strategy but I agree with one of the comments following the article. It is much too cynical to view the issue primarily as a wedge in the 2014 election. It should be a fundamental principle that the party would fight to pass even if it were not supported in the polls. The Democratic Party should be in the business of convincing the public to do the right things that serve the public interest.