In the 2008 presidential election, 80% of adults from families earning at least $100,000 a year voted, while only 52% of adults from families earning $20,000 or less cast a vote, according to data from the Census Bureau.
Married homeowners with college degrees are also far more likely to vote than single renters with high school diplomas. Older people are often more politically involved, while younger voters -- who tend to skew lower in income -- may not feel as tied to a community, and vote less frequently.
One reason for the voting disparity is that lower-income people tend to be less educated and not as politically active in general. In contrast, wealthier people are often better connected to donors, community leaders and politicians who encourage them to vote.
"People with more income are likely to feel like they have more at stake in terms of taxes, public services and various benefits," said Lane Kenworthy, professor of social and political science at the University of Arizona. "People with lower incomes are more likely to feel disillusioned, because they tend to feel like policy never changes."
Why the poor should be voting more
Some people argue that the lower income groups are the ones who need the most help from government, while others feel that they aren't politically savvy enough to take on the responsibility.
When the Electoral College was created in 1789, some feared that the uneducated, agrarian masses could not be trusted to elect a qualified leader, and wanted Congress to choose the president instead. The Electoral College was created as a compromise between the two options.
"Lower income people tend to be less politically informed, so people have long argued that maybe it's just as well that they don't vote," said Andrew Gelman, a professor of statistics and political science at Columbia University.
"But to the extent that the government is supposed to represent people equally, then it is a problem that low income people aren't as represented," Gelman added.
Widening income inequality and high unemployment since the recession have put more economic pressure on the lower income groups. Workers with just a high school degree have an 8.8% unemployment rate. For workers with a bachelors degree or higher, only 4.1% are out of work.
Those who do vote the most -- the rich -- tend to vote Republican in most elections, Gelman said.
But in 2008, a small segment of that group bucked the broader trend.
Exit polls conducted for CNN show that, in addition to winning the majority of voters earning under $100,000 a year, Obama also won over the majority of the rich -- those earning $200,000 a year or more.
"Obama had a lot of appeal to richer voters. He was very well educated, he had an urbane style, a lot of his supporters were from the high-tech and financial industries," Gelman said. "McCain really had less of that, and as a candidate, he and Sarah Palin, had an anti-elitist message which made them less appealing to rich people."
A Gallup poll conducted last week shows the richest tier of voters are again supporting a Republican ticket. Those with a household income of $120,000 or more are leaning in favor of Romney, whereas households earning less than $48,000 are leaning toward Obama.
The middle class, however, is still up for grabs. It's no wonder then that both candidates are focusing so heavily on trying to win over middle-class voters.