Some contemporary and modern historians, politicians and economists believe the U.S. was effectively plutocratic for at least part of the Gilded Age and Progressive Era periods between the end of the Civil War until the beginning of the Great Depression. Zinn's books: https://www.amazon.com/gp/search?ie=UTF8&tag=tra0c7-20&linkCode=ur2&linkId=442953955d9f3e70404880768f217c8e&camp=1789&creative=9325&index=books&keywords=howard%20zinn
After the Civil War, with large industries reaching monopolistic or near-monopolistic levels of market concentration and financial capital increasingly integrating corporations, a handful of very wealthy heads of large corporations began to exert increasing influence over industry, public opinion and politics. Money, according to contemporary progressive and journalist Walter Weyl, was "the mortar of this edifice", with ideological differences among politicians fading and the political realm becoming "a mere branch in a still larger, integrated business. The state, which through the party formally sold favors to the large corporations, became one of their departments."
In his book The Conscience of a Liberal, in a section entitled The Politics of Plutocracy, economist Paul Krugman says plutocracy took hold because of three factors: at that time, the poorest quarter of American residents (African-Americans and non-naturalized immigrants) were ineligible to vote, the wealthy funded the campaigns of politicians they preferred, and vote buying was "feasible, easy and widespread", as were other forms of electoral fraud such as ballot-box stuffing and intimidation of the other party's voters.
In modern times, the term is sometimes used pejoratively to refer to societies rooted in state-corporate capitalism or which prioritize the accumulation of wealth over other interests. According to Kevin Phillips, author and political strategist to U.S. President Richard Nixon, the United States is a plutocracy in which there is a "fusion of money and government." A similar position was taken by the Fourth International in January 1941, which stated "Roosevelt's administration, which claims to be democratic, is really the representative of these piratic plutocrats" and that "the twin capitalist parties control all the main avenues for reaching the masses (the press, radio, halls, etc) …they collect millions from their wealthy masters and spend them to bamboozle the public and buy elections".
The U.S. instituted progressive taxation in 1913, but according to Shamus Khan, in the 1970s, elites used their increasing political power to lower their taxes, and today successfully employ what political scientist Jeffrey Winters calls "the income defense industry" to greatly reduce their taxes.
Chrystia Freeland, author of Plutocrats: The Rise of the New Global Super-Rich and the Fall of Everyone Else says that the present trend towards plutocracy may not be a deliberate power grab:
You don't do this in a kind of chortling, smoking your cigar, conspiratorial thinking way. You do it by persuading yourself that what is in your own personal self-interest is in the interests of everybody else. So you persuade yourself that, actually, government services, things like spending on education, which is what created that social mobility in the first place, need to be cut so that the deficit will shrink, so that your tax bill doesn't go up. And what I really worry about is, there is so much money and so much power at the very top, and the gap between those people at the very top and everybody else is so great, that we are going to see social mobility choked off and society transformed.
— Chrystia Freeland , NPR
When the Nobel-Prize winning economist Joseph Stiglitz wrote the 2011 Vanity Fair magazine article entitled "Of the 1%, by the 1%, for the 1%", the title as well as the content pointed to evidence that the United States is increasingly ruled by the wealthiest 1%.