Two new studies by political scientists offer compelling evidence that the rich use their wealth to control the political system and that the U.S. is a democratic republic in name only.

In a study of Senate voting patterns, Michael Jay Barber found that “senators’ preferences reflect the preferences of the average donor better than any other group.” In a similar study of the House of Representatives, Jesse H. Rhodes and Brian F. Schaffner found that, “millionaires receive about twice as much representation when they comprise about 5 percent of the district’s population than the poorest wealth group does when it makes up 50 percent of the district.” In fact, the increasing influence of the rich over Congress is the leading driver of polarization in modern politics, with the rich using the political system to entrench wealth by pushing for tax breaks and blocking redistributive policies.

At the turn of the decade, political scientists Larry Bartels, Jacob Hacker and Martin Gilens wrote several incredibly influential important books arguing, persuasively, that the preferences of the rich were better represented in Congress than the poor. After the books were published, there was a flurry of research arguing that they had overstated their case.

Critics alleged two key defects in Bartels’ and Gilens’ arguments. First, because polling data on the super-wealthy were sparse, it was difficult to prove that there were large differences in opinion. Political scientists often rely on composite measures of policy liberalism, but since the poor tend to be more economically liberal but socially conservative, the differences between the poor and moderately rich can often be obscured. Second, there was no way to show that influence of the wealthy was caused directly by the influence of money. It might well be that the rich are simply opinion leaders or are more likely to vote.

Recent research offers compelling answers to these criticisms. The new evidence adds credence to the Bartels-Gilens-Hacker view that money is corrupting American politics. By using a massive database of ideology that includes the super wealthy, Schaffner and Rhodes found that “members of Congress are much more responsive to the wealthy than to their poor constituents.” However, this difference is not equal between both parties; rather, Democrats are far more responsive to the poor than Republicans. (This is not surprising; other research supports this claim . ) They find that both parties strongly favor the upper-middle class, those with $100,000 to $300,000 in wealth. But Republicans are not only more responsive to the rich, but particularly to rich donors. Schaffner and Rhodes argue that, “campaign donations, but not voter registration or participation in primary or general election, may help explain the disproportionate influence of the wealthy among Republican representatives.”

Barber’s study is the first to directly examine the policy preferences of the donor class. Barber sent 20,500 letters to people who contributed to 22 Senate elections in 2012 and asked about various policy questions. This allowed Barber to examine the differences in representation between donors and non-donors. His finding: Donors’ preferences tend to be far better represented than non-donors’. The chart below measures the ideological differences between various groups, with 0 indicating a perfect fit. The data show that Senators are almost perfectly aligned with their donors, but rather distant from voters.