Given that the political_line parameter is used for both single political ideologies and lists of political ideologies; I think the parameter should be renamed to political_lines (and in name, Political line(s)).
Better yet, I don't see why we could just rename political_lines to political_ideologies.
Political orientation works even better imo. We should go with that.
Of course, I'll implement the change to be backwards compatible to give time for our comrades to adjust.
There, I made the changes and batch edited all articles containing political_line to political_orientation (with a reflection on the infobox header too)