For it to be partisan rhetoric, one would have to think that some level of her constituency would believe such a thing, no? Is it such a leap to conclude that she might believe it as well?
Just like with the knucklehead who may or may not have actually been worried about an island sinking, how are we to know what these people actually believe anymore? She may not be stupid, but it is certainly dumb for a congressperson to suggest their constituents shouldn't fill out the senate at a time when Minnesota could lose a seat or two in Congress if it were undercounted.
Incidentally, she ceased her anti-census rhetoric when that came to light, so maybe she isn't a dummy after all.