Emperor Palpatine holds the distinction of being the single most sinister character in a universe sporting a bumper crop of them. Star Wars has always thrived on its villains, starting with Darth Vader’s iconic entrance at the beginning of Star Wars: Episode IV – A New Hope, and yet the Emperor has always been first among equals. That applies not only to his temporal power -- ruling the galaxy with an iron fist for nearly two decades -- but his Force abilities as well. The latter directly feeds into the former more than once.
That crops up in subtle ways as well as overt, particularly in the prequel trilogy when he must act discreetly or else draw the attention of the Jedi. Even so, he wasn’t exactly difficult to spot. How was it that he could fool so many people -- particularly Force users -- for so long? It turns into a bit of a Clark Kent question, as the politician known across the galaxy can hide his identity simply by pulling a hood over his head and speaking with a sinister voice. The easy answer to the conundrum is that he used Force powers to do it.
“The Force can have a strong influence on the weak-minded,” Obi-Wan famously said in A New Hope, and the Force Persuade has been a staple of Jedi powers ever since. Sith Lords rarely display it onscreen -- relying on far less subtle abilities like Force chokes -- but it stands to reason they could use it as well if they wished. Palpatine could presumably make effective use of it as a politician, allowing him to gently wheedle people into adopting his position simply by “suggesting” it very strongly. Indeed, his seduction of Anakin in Star Wars: Episode III – Revenge of the Sith bears the trademarks of Force Persuasion, along with the hypnotic lights of the opera they’re ostensibly watching. The fingers of his left hand even twitch slightly as he speaks to Anakin.
And he needn’t be subtle with it, either. According to the canon novel Lords of the Sith by Paul S. Kemp, his powers of suggestion are so strong that he can take over their minds completely and induce them to obey his commands. Such a figure would have no problems erasing or altering memories to suit him. The same novel also details his unerring accuracy at predicting the future, which included a few obvious blind spots, but would otherwise allow him to anticipate those who could identify him and prepare some manner of countermeasures.
Add to that the Jedis’ diminished power to use the Force, as Yoda and Mace Windu discussed in Star Wars: Episode II – Attack of the Clones. A figure as powerful as Palpatine could more readily hide his Force presence in such conditions and would happily take advantage of it as needed. With the dark side ascendant, it became all the easier to move undetected in the guise of a far more benevolent façade, using his prescience to avoid Jedi who might notice him and relying on his Force Persuasion or simple brute mind control for any other situation.
But the final and most powerful aspect of it all had nothing to do with the Force, but rather Palpatine himself, whose brilliant duplicity is rarely commented on. Until the very end, his surface demeanor remains benevolent, and for the bulk of the Clone Wars, the Jedi actively defend him as the legitimate head of state. He actually appears rather impotent much of the time, with a quavering voice and a faux humility that makes it easy to believe that he’s little more than an efficient paper pusher with good intentions. The idea that he could be a Sith Lord becomes difficult to accept on its face, and a few quiet uses of Force powers could easily make the impression permanent.
The Emperor always represented the threat from within in Star Wars: engineering a crisis as an excuse to seize power rather than conquering the galaxy with an army. His Force powers inevitably played a huge role in that, but in the end, he kept his true nature hidden the same what any good con artist did. He fooled them because they wanted to be fooled. Using the Force just made sure he could close the deal.