There may have been. What we know for certain is that in July of 1933 Marine Corps Major General Smedley Butler was approached by Gerald MacGuire, a bond seller for a New York brokerage firm, and Bill Doyle, the president of the Massachusetts branch of the American Legion. Doyle's and MacGuire's avowed purpose was to encourage Butler to run for nationwide president of the American Legion. According to Butler's later testimony, they were actually interested in using him to command a column of several hundred thousand veterans. The column was to march on Washington and force President Franklin Roosevelt to surrender most of his powers of day-to-day domestic governance an "executive vice president". The justification for this alleged plot was apparently FDR's decision to get America off the gold standard. According to Butler, the logic followed by the two men was that such a decision threatened American's economic stability with inflation. Economic instability, in turn, threatened the prosperity and well-being of America's veterans, a group that Butler had publicly expressed sympathy for. He had gone so far as visiting the Bonus Army encampment just days before General MacArthur drove it from Anacostia Flats. General Butler went public in late 1934 with accusations about the alleged coup attempt, which then Congressman Fiorello LaGuardia described as the "cocktail putsch". In November 1934 he testified against MacGuire and Doyle before the House Special Committee on Un-American Activities.

All this begs, of course, several questions:

1. Was there a credible attempt at a coup? This question probably deserves a qualified yes. There was solid circumstantial evidence that the meetings between Butler and the alleged co-conspirators occurred. In addition, evidence showed that MacGuire had visited Europe during this period, and had sent letters back to Doyle describing the structure and operations of european fascist movements such as the Croix de Feu in France. However, it is uncertain how much real support MacGuire had in wealthy circles. Some contemporaries speculated that he was merely a reckless adventurer with a gift for gab. Witness Congressman LaGuardia's dismissive "cocktail putsch" comment. This also seems to be the opinion of later historians
2. Why choose Butler? General Butler was probably the most publicly visible professional soldier in the United States after Douglas MacArthur and John Pershing. While he hadn't fought in World War I, he had taken part in the Spanish American War, the Philippines Insurrection, The Boxer Rebellion and U.S. invasions of Haiti, Mexico, and Nicaragua. He was twice awarded the Congressional Medal of Honor for these exploits. Even Butler's critic's gave him credit for physical courage and coolness under fire. A good summary of Butler's career, including his role in uncovering the MacGuire plot, can be found in this article: "Matter of Fact -- Ollie and Old Gimlet Eye", by Geoffrey C. Ward, American Heritage Magazine, November, 1987, vol. 38, no. 7. A video stream of Butler testifying before the Special Committee can be found at https://en.wikipedia.org/wiki/Business_Plot
3. Did the alleged coup have any chance of success? Probably not. It was simply too ambitious. Mobilizing half a million veterans, and getting them to march on Washington, had too many working parts that had to be synchronized. It was probably impossible to advance this sort of operation any further than it had been while maintaining secrecy. In addition, it seems unlikely that many veterans would have cooperated. True, President Roosevelt failed to give World War One veterans early access to their bonus money, as had President Hoover before him. However, he did prove willing to give them and other Americans the opportunity to work, through the Worker's Progress Administration. He also extended this opportunity to their teenage children through the Civilian Conservation Corps. Veterans probably saw enough of a difference between Hoover and Roosevelt to make them unwilling to back such a coup. Still, even a failed coup attempt could have had a demoralizing effect on an America already reeling from the Great Depression. Butler probably performed a public service by exposing MacGuire and Doyle.