Yes.
Well, technically it is a parliamentary republic at the moment, but it has historically been the most democratic country in that part of the world for about a thousand years. I think that has been its main problem. Too much democracy made them easy targets for Germany, Russia, Austria, etc., over the past several centuries.
It's interesting (and from my national point of view, depressing) how diffrently the two European countries with early parliamentary system (England and Poland-Lithuania) evolved.
being an island and being "sandwiched" between two reactionary super-powers tends to do that.
Except at the time I've mentioned Brandenburg/Prussia was a minor German state and Russia used to be a favorite target for Polish-Lithuanian interventions. What you are refeering too came later, because we f**ked up our status as a major power.
Hell, didn't the Duchy of Prussia start out as a Polish-Lithuanian tributary?