It's written somewhat dishonestly, you have to read down past the sensational first couple of paragraphs to discover that much of this lack of influence come from people failing to vote. For example:
America's turnout rate places us near the bottom of industrialized democracies. More than 90 million eligible Americans did not vote in the presidential election of 2012 and more than 120 million did not vote in the midterm elections of 2010.Voting is free and requires only the ability to read. Whose fault is it that the poor do not vote in large numbers? I conclude the fault is their own. Hat tip to Lucianne.com for the link.
Electoral turnout in the United States is highly correlated with economic standing: The more affluent Americans vote in much higher proportion than the less affluent. A study by Ellen Shearer of the Medill School of Journalism at Northwestern found that 59 percent of 2012 voters earned $50,000 or more per year, compared to 39 percent of non-voters. Only 12 percent of non-voters earned more than $75,000, compared to 31 percent of voters.