Their whole job is to 'represent' their constituents. A LLM can poll the sentiments of the people far more effectively than they can. I'm sure it could be programmed to accept bribes too to weigh rich people's opinions higher. I'd love to see votes done by 100 different LLMs instead of Senators (a hyperbolic, non literal statement but interesting as a thought experiment I hope)
Politicians should still propose new and altered legislation but actually voting, and being informed to vote, could be massively improved.