Spygate (conspiracy theory)
Spygate is a disproven conspiracy theory peddled by 45th U.S. president Donald Trump and his political base on many occasions throughout his first presidential term. It primarily centered around the idea that a spy was planted by the Obama administration to conduct espionage on Trump's 2016 presidential campaign for political purposes.
Source: Wikipedia — Spygate (conspiracy theory) (CC BY-SA 4.0)