Do the leaves have a rank smell when crushed?

Nothing that slaps me in the face, but how "rank" do you mean, comparatively speaking? Have had stinkhorn mushrooms pop up after cool, rainy stretches and to me that stench is the definition of rank.

Sort of strong smelly herbal scent, not a putrid pong.

Gotcha. Will double-check and let you know.

putrid pong <<<--- sounds like a new frat game

There's a smell that, to me, is a bit herb-y, and a tiny bit earth-y. Overall not strong, though. Is that any help at all?

It eliminates one plant I thought might be it.

floral_uk: What did you think it might be? It was 50 degrees F when I crushed the leaves. Maybe the smell would be stronger in warmer temps?

peren.all: Funny you should mention campanula. Been trying to get rid of what looks like campanula rapunculoides (creeping bellflower) since we moved here. Its leaves are slightly more pointed, though, and the plants to date haven't spread uncontrollably. Just a few sprout up every season, usually in different spots.

I was wondering about a Betony of some kind. Maybe you'll have to leave one and see if it blooms.

Looks like Campanula glomerata to me too.

It resembles Hesperis matronalis to me.

But that doesn't have felted leaves and nor does it spread by underground runners.

Looks like lily of the valley.

Nope. Lotv is not felted, nor serrate, nor ovate and it has the parallel veining of a monocot.

As suggested, left some of the plants alone this growing season. They grew maybe 2-4 inches taller, never produced buds or blooms, only spread. Dug out the runners as best I could and will see what the few remaining plants do next season. Thanks for all the suggestions. A puzzler for sure.

Chrysogonum virginianum perhaps?