A new book "Hunting the President: Threats, Plots, and Assassination Attempts - from FDR to Obama" (Regnery) by Mel Ayton shows that assassination attempts and threats are far more common that it is know.
According to New York Post, some assassination attempts we either never learned about, or which were written off by the media as minor, came shockingly close to achieving their goals, some even before the president in question could take office.
The book reveals that every president, regardless of party or ideology, is faced with thousands of threats on file at any moment, with nearly 400 or so regarded as serious.
In order to get funding, Crawford approached both the KKK and Jewish groups, who alerted the FBI, who sent undercover agents to infiltrate the plot.
While the duo was arrested after their plans were foiled by the FBI following a tip off, later the prosecutor said that the device they built "would have been capable of emitting X-ray radiation that would have caused death" and only failed to do so because the undercover agents had provided them with faulty parts.