you cannot - I repeat cannot - move the Overton window left by voting for right-wingers.
Yes you can. You can lower the temperature of something by pouring over it something hot, but less hot than what you’re trying to cool down.
In the same way, voting for a right-winger over a far right-winger will shift the Overton window to the left. Because left and right are relative terms, like the other guy was trying to say.