Protectionism is neither "left" nor "right", its essentially an orthogonal axis. There are dissenters from the broad neoliberal trade consensus across the left/right spectrum. (Generally, the main dissent on the left
favors international trade agreements, but favors stronger common labor, human rights, and environmental protections that are common in the current international regime, with tariffs as a fallback if they can't get these kinds of deals; the dissent on the right is more likely -- like Trump -- to see tariffs as a tool more directly to deal with trade imbalance, to see it about a weapon for "winning" trade.)
Not everything that disagrees with the dominant position of the Republican Party is "far left".