Apparently, if you decide to oppose someone and that person happens to be Jewish, then yes, you are now anti-semitic.

In some cases, maybe, I do think anti-Semitism is bipartisan. But I don't think it's the driving factor for either the left or right (in the US,) that's more of the fringe. I would be willing to bet most people who know of Soros and don't like him, have no clue he's jewish.