Ive found Twitter leans left by about a ratio of 10 to 1.
However the volume of users is sufficiently large that you can be swamped by any minority if you choose, no matter how tiny.
“left-twitter” simply designates a subcommunity within twitter. I don’t think OP meant that Twitter as a whole leans left. Many people have an opinion on that topic, but in reality it’s hard to know for sure as Twitter is very large.
Just because the most egregious and dangerous stuff from one side gets deleted does not mean it's a place only for the polar opposite.