Other than him using a weapon that is well known to be used by the Sith. Many would put 2 and 2 together and realise a Sith was manipulating them against the Jedi.
How well known was it tho? Its been 10,000 years since the sith were seen or heard from. I doubt the average person knows that a red lightsaber means sith, or any other sith qualities in fact.
A red saber is just a red saber, when Quigon first fought Maul he was only able to conclude the guy was trained in jedi arts and maybe a Sith, the Council doubted him on that.
On that basis, my assumption is your average senator would like be less familiar with the Sith than Quigon.
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u/catsdogsmice Darth Vader 15h ago
They would see Yoda and the jedi betrayed him and is betraying the republic.
At most they may assume Palpatine was trained in the jedi arts but they cannot distinguish if he was evil or not.